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NOAO CCD MOSAIC IMAGER USER MANUAL (KPNO Mosaic

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1. Well doobs is for you With this task it is possible to take flat fields or exposures of the same object in a list of filters The major limitation for taking flats is that the lamp brightness level will be the same for all exposures For example cl gt doobs Exposure type object dflat sflat df Number of exposures to take in each filter 1 1 5 list of filters in wheell B V R I List of exposure times 15 10 5 The following pictures will be taken PicturesFilterlExposure 31 35B15 36 40V10 41 45R5 41 4515 Title for pictures Dome flats nightl Filterl BTelfocus 9300 0000 38 Images dflat031 dflat035 Mosaicl 1 8315 1 8220 bin 1 1 gain 1 Sequence finished Filterl ITelfocus 9300 0000 Images dflat041 dflat045 Mosaicl 1 8315 1 8220 bin 1 1 gain 1 Sequence finished All exposures finished will take sequences of 5 dome flats each in B 15s exposures V 10s and R and I 5s each Note that the list of exposure times may be shorter than the list of filters in this case the last exposure time is used for all the remaining filters as in the example The list of exposure times can also be longer in which case multiple exposures of different times will be taken in the last filter Thus for instance a list of filters of B and a list of exposures of 30 300 would take a 30s and a 300s exposure in the B filter Note that doobs is simply a cl script ba
2. Figure 4 11 1 The main GUI panel for the DCA Verify that the directory shown is where you want your pictures to go controlled via the Arcon IRAF window using cd You can watch the packets count up as the picture is read out Briefly the Main DCA GUI provides control for you to 1 turn on or off the auto display of images Display Enable box as they are being read out Turn this off for very short exposures e g biases 2 enable the post acquisition processing Postproc Enable 3 allow auto termination of the current display process if another image is read out before the previous display completes Auto Kill Enable You can also monitor the status of the readout bottom line gives percent of readout and verify that the filter and image type are correct 42 wv WISH SUA TSE Sel x SCDISPLAY Paraneters ts M Do Display Processing Fiat Fields J Flat Field Overrides DCA Setting of Filter Postpone Display Until Readout Conpletes Delay EE nvironnent Readout Before fz Stdinage int4400 Node Display Begins Display Extns eA e RIA 1 2 Suitch Display to All Hone Frane Being Loaded 2 Scaling zscale zrange 23 jo z 1000 zconbine auto Figure 4 11 2 The Display Options Editor GUI panel for the DCA This GUI offers control of several complex functions The Display Options Editor panel allows you to 1 enable on
3. At the 4 m 4 inch filters illuminate approximately 5 5K X 5 5K pixels 46 of the total sky area The positioning of the filter track is highly repeatable However the acceleration of the track can occasionally dislodge dust particles between filter moves particularly if intervening movements have turned the filter upside down In all cases the filter track software moves the track in the direction that minimizes the distance moved to reach the requested filter position In addition to the 14 position filter track there is a manual slide that can hold a single filter of the same size 5 75 inches square This may be used for example to hold a bandpass filter when polarization filters are used in the track Use of an additional hand insert filter changes the focus At the 4 m changing inserting or removing this filter can only be done at the maintenance Southeast Annex position 3 6 Filters For Mosaic To fully utilize the field of view of the 8Kx8K filters must be 5 75 inches 146 mm square and have 5 43 inches 138 mm clear aperture The optimum thickness that preserves image quality over the entire field of view is 0 47 inches 12 0 mm All NOAO mosaic filters adhere to these specifications to maintain a parfocal condition Thus neither the telescope nor the guide TVs should require a focus change when switching between filters There is one exception the CuSO U filter 14 k1001 for which there is a focus offset
4. 2 fill The MSCDISPLAY task is based on DISPLAY with a number of specialized enhancements for displaying Mosaic data It displays the entire Mosaic observation in a single frame by filling each image in a tiled region of the frame buffer The default filling defined by the order parameter sub samples the image by uniform integer steps to fit the tile and then replicates pixels to scale to the full tile size The resolution is set by the frame buffer size defined by the stdimage variable An example command is cl gt mscdisplay obj123 1 Many of the parameters in MSCDISPLAY are the same as DISPLAY and there are also a few that are specific to the task of displaying a mosaic of CCD images The mapping of the pixel values to gray levels includes the same automatic or range scaling algorithms as in DISPLAY This is done for each image in the mosaic separately The new parameter zcombine then selects whether to display each image with it s own display range none or to combine the display ranges into a single display range based on the minimum and maximum values minmax the average of the minimum and maximum values average or the median of the minimum and maximum values The independent scaling may be most appropriate for raw data while the minmax scaling is recommended for processed data Another new optional answer here is auto which is the default will try to use the best option given the status of the data There is a n
5. 4m and WIYN 0 9m Mosaic 2 at the CTIO 4m also differ in some specifics This manual contains much information that is common to both cameras but is focused on the specifics of using the Mosaic 1 at the KPNO 4m and WIYN 0 9m Arrays Pixels size Read noise DQE Dark current General Characteristics 8 2048x4096 SITe CCDs thinned science grade 8192 x 8192 16 bits plus header overscan 135 Mbytes 15 um 0 26 pixel at the 4 m 0 43 pixel at the 0 9 m 6e 86 peak at 6500A average for 8 CCDs see also Figure 3 1 2 5 e pixel hr Read out 2 minutes 34 seconds 1 min 6 sec when binned 2x2 time including overhead CCD Gaps 0 7 mm 50 pixels in rows 0 5 mm 35 pixels in columns Cosmetics Good to excellent typically 2 bad columns per CCD but many 2 8 pixel areas of 5 variation flatfield completely and some very large areas of 10 variations that all flatfield to lt 0 5 Filters 5 75 x5 75 parfocal 34 filters now available at KPNO a list of all available filters can be found here http www noao edu kpno mosaic filters filters html UBVRI see Sec 2 6 Saturation Typically linear to 0 1 to 70 000 e Gain 3 e ADU Count Rates FOV Scale Image quality Artifacts Typical focus ADC KPNO Mayall 4 Meter Parameters At UBVRI 20th mag U 35 B 330 V 340 R 410 I 225 e sec 36x36 XIMTOOL Orientation North left East down 0 26 pixel at center decreases q
6. MSCSTACK When conditions are favorable however we have produced beautifully flat stacked images free from defects showing the full scientific potential of Mosaic camera and providing a suitable reward for our hard work 5 10 A Simplified Summary of the Processing Steps George Jacoby contributes the following sequence It represents as simple a sequence as makes sense for dithered Mosaic images taken under good conditions I CCDPROC to correct for cross talk trim overscan bias subtraction and flat fielding Il MSCZERO apply a uniform astrometric zeropoint to all images of all colors in a sequence dithered or not Identify a star in each frame and set its zeropoint to be identical IM MSCZERO using the w key identify 10 20 stars per CCD in one of the frames in the sequence IV MSCCMATCH correct for rotations and minor zeropoint offsets I run this interactively to be sure the solutions are good V MSCIMAGE select a single image that will serve as a reference for all other images of this field All other images will then have the correct geometry for stacking and later comparison VILMSCSTACK add up the dithered sets VILIMCOPY up to this point you have created single images constructed from the 5 or more images in each of the dithered sets Because each image stared at a different piece of sky there will be offsets between the images and each image may have a unique size I use IMCOPY to select a region of
7. Nutmeg KP4m mtc dev nstO DDS4 DAT Nutmeg KP4m mta dev nst2 DLT 7000 Tan KP4m mtb dev nstO EXABYTE Tan KP4m mtc dev nst1 DDS4 DAT Emerald W0 9m mtb dev nst1 EXABYTE Emerald W0 9m mtc dev nst0 DDS4 DAT Emerald W0 9m mta dev nst2 DLT 7000 52 5 5 The Reduction of Mosaic Images The reduction of Mosaic camera images at first glance is just like that of any other CCD camera ignoring the immense amount of data contained in a single Mosaic image As is standard for other cameras reduction requires overscan correction followed by zero and flat field corrections In detail however full reduction of Mosaic data requires a number of steps not normally encountered in the routine reduction of other CCD camera images The driving factor in Mosaic reduction is the expectation that the observer will not simply obtain a single Mosaic exposure of an astronomical field but may want to construct a deep integration from several Mosaic images spatially offset or dithered from each other to cover both the gaps between the individual CCDs and any defects Stacking dithered Mosaic images places high demands on the uniformity of the initial data reduction as well as requiring several additional steps once the basic reduction of the individual exposures is complete See Buell Jannuzi s Draft Guide to NOAO Deep Wide Field Sruvey MOSIAC Reductions http www noao edu noao noaodeep ReductionOpt frames html for more information on Mosaic data r
8. Some of the currently available filters and approximate count rates e sec for a 20 mag star are Filter R I H H 4 H 8 H 12 H 16 S1 SDSS g SDSS r SDSS 7 SDSS z Om 2 ON1 29 2 White Wash M Wash C DDO 51 WR CM WR Hell WR 475 WR CIV TV S8612 BG 38 BK 7 RG 610 BK 7 BK 7 BK 7 BK 7 BK 7 BK 7 BK 7 BK 7 BK 7 BK 7 BK 7 BK 7 BK 7 BG 38 S8612 BK 7 BK 7 BK 7 BK 7 BK 7 Peak T BS 69 3 88 4 86 2 93 9 94 3 ot 89 5 86 1 90 7 90 2 91 8 94 6 94 8 T2 90 5 972 87 1 75 4 85 1 68 4 73 3 78 8 12 7 Central Wave 3577 4360 5370 6440 8220 6569 6611 6650 6692 6730 4813 6287 71132 9400 5021 5305 5600 5100 3860 5132 4653 4690 4750 5816 4 m FWHM 15 646 990 940 1510 1930 80 81 81 81 80 1537 1468 1548 2000 55 241 6800 1140 1034 161 52 51 51 46 e s 35 330 340 410 225 Central Wave 3577 4360 5370 6440 8220 6575 6615 6656 6695 6736 4813 6287 71132 9400 5027 5305 5600 5100 3860 5132 4660 4695 4755 5823 0 9 m FWHM 647 990 940 1510 1930 80 81 81 81 80 1537 1468 1548 2000 53 241 6800 1140 e s 14 15 16 See Figures 3 6 1 through 3 6 5 for plots of the current filter transmission curves ASCII Tables that describe the transmissions are available on the Mosaic Web Pages The U b
9. et al 1998 SPIE 3355 721 for a detailed description of the corrector and ADC j CoO Figure 3 8 1 The 4 m corrector optical layout All elements are made from fused silica except for the ADC components which are made from LLF6 UBK7 LLF6 and UBK7 as viewed from left to right At the right are the science filter dewar window and CCD from left to right The ADC elements appear in the middle as 4 planar elements although they are wedged The 0 9 m corrector is a simple 2 element fused silica design There is no ADC at the 0 9 m See Figure 3 8 2 below for the optical layout 21 Figure 3 8 2 The 0 9 m corrector optical layout Both elements are made from fused silica At the right are the science filter dewar window and CCD from left to right Coatings and Scattered Light All optics have been coated with very broad band multi layer anti reflection coatings to improve photon collection efficiency and to reduce scattered light Surface losses are 10 from below 3500 A to longward of 9500 A at the 4 m and better at the 0 9 m In addition all interior structural surfaces have been blackened to minimize scattered light Tests at the telescope indicate that the new correctors suffer significantly less than the old correctors from scattering Nevertheless with the very wide fields being imaged bright stars are inevitable producing some ghosting from bright objects in certain fields Image quality The 4
10. is initially written in the controller s internal format to a spool file but it is automatically converted into a FITS format image on tan emerald within a few seconds of the exposure finishing The end of each exposure is accompanied by distinct sound from tan s speakers If you requested that observe take only a single exposure the message observation finished will appear in the IRAF interface window as soon as the readout is complete things are then ready for you to start another exposure If instead you requested a sequence of several pictures the next exposure will start automatically You may immediately examine or process the resulting image even though the sequence is not complete Note that the pictures remaining counter in the status window shows how many exposures remain in the sequence Once the final picture has been readout the message sequence finished will appear in the IRAF interface window Should you miss the end of sequence or end of exposure message note that the CCD is idle and things are ready for you to initiate new exposures whenever the top line of the status display reads CONTINUOUSLY_ERASING 36 4 9 Exposure Control Commands The following commands can be used to modify an ongoing exposure e pause Pause the exposure e g while waiting out passing clouds e resume Resume a paused exposure e tchange Change exposure time You will be prompted for the amount by which to ch
11. new frame will be displayed into 8 choose whether the display screen will switch to the frame showing the new data automatically if you are examining an earlier image the change to the new picture is disconcerting 9 adjust the delay before display begins usually 7 of the picture is enough the display program must collect some data to determine the data range before showing you the image otherwise the image might appear all white or all black causing great but unnecessary concern about the data Path Parameters Display Cmd i raf msgbus bin mscdisplay Postproc Cmd i raf msgbus bin postproc Calibration Dir i raf fextern mscdb noao kpno 36inch caldir Reset Apply Help Done Figure 4 11 3 The Path Options Editor GUI panel for the DCA This GUI controls the names of commands and locations of files Normally you never need to see this panel If you change the command names for the display task or the postprocessing script you are flying solo In order to calibrate new images as they are being read from the Mosaic on the fly typical biases and flatfield images are kept in a directory The Calibration Dir allows you to change the location where these images are stored We are developing tools so that the average user can build the specially processed and compressed flat field images used by the display processor When these are completed it may be useful to construct your own directory of flats For now adjust
12. the 19 distribution panel see Figure 3 7 1 For the selected TV on the ICCD Control Panel Turn the high voltage potentiometer completely counterclockwise 10 turn pot Toggle the power switch on on TV screen pixel defects will appear Neutral density switch should be down off Push the momentary button to enable high voltage Slowly turn the high voltage potentiometer clockwise monitoring TVs until guide stars appear Acquire a guidestar on the computer moss and initiate guiding consult the 0 9 m telescope user s guide http www noao edu 0 9m Tel_Op html for details on step 6 ai a a a a When switching between the two TVs be sure to turn the high voltage potentiometer counterclockwise and turn off high voltage on the TV no longer in use ICCD 8 SOUTH ICCD A NORTH LN OO0000 MONITOR N39 INAS D oO mm a D oi NORTH SOUTH 9 METER ACQUISITION TY SYSTEM Figure 3 7 1 A schematic drawing of the layout of the TV control panels at the 0 9 m Only the two leftmost panels in the lower rack are used with the Mosaic TVs The upper rack is used to select which TV video signal is seen on the monitor 20 3 8 Correctors The 4 m corrector is a 4 element fused silica for maximum U band efficiency design with additional internal prisms that serve as an atmospheric dispersion corrector ADC See Figure 3 8 1 below for the optical layout and refer to Jacoby
13. the mode from the first pass to limit the range of allowable values to between zero and twice the initial mode With good zero dark and flat field images in hand the basic image reduction is done with the MSCRED version of CCDPROC If your data consists of a dither sequence that you intend to stack later we recommend that you do not interpolate over bad pixels this is more logically done downstream as we discuss later One of the last basic steps that you may attempt is to build a sky flat or illumination correction from a portion of your reduced data You could try going directly to a sky flat without any prior reduction with a dome flat or any other serviceable flat but working with roughly flattened data first allows for more accurate estimation of the mode in the presence of faint astronomical sources and further allows for better detection and rejection of biased regions of the images At the same time flat field reductions will produce wild values in the few defect regions so extra care is required when estimating modes or other statistics from flattened data 5 8 The Variable Pixel Scale and Zero Point Uniformity A key assumption in traditional reduction of CCD images is that the pixel scale is uniform and that a properly reduced blank sky image will have a uniform and flat appearance This is not correct when the pixel scale varies over the field In the case of Mosaic the pixel scale decreases approximately quadratically from
14. the fly processing overscan subtraction flat fielding of the raw image flat fielding applies to object types only to provide a cleaner image for quick look examination otherwise sensitivity variations across the chips make it very hard to see faint objects This option requires about 20 CPU seconds beyond a simple display of the image It does not affect the saved data but only the appearance of the displayed imaged 2 override the flat field to be used in the on the fly processing You must pull down the proper filter name prior to the start of readout in some cases the proper flat field may not be available for the filter you are using but a recommended alternative can be used noted with the gt sign 3 postpone the display until full readout is complete Display After Readout Completes this option provides a speed advantage when displaying over a network to another computer 4 change the resolution of the display Stdimage to speed up the display process or to improve the visual look of the display smaller imt numbers make the display faster but average more pixels together when displaying the image thereby losing resolution 43 5 change the Node or name of the computer being used for the display normally this is the same computer that the DCA runs on usually tan or emerald and no entry is needed here 6 preset the primary display parameters zscale zrange z1 z2 7 select which frame the
15. this parameter at your own risk 4 12 Observing in Binned Mode Some science programs need the full field of view of MOSAIC but greatly need to reduce the amount of over head in taking an image down to 1 06 from 2 34 for 2x2 binning If you do not need the full spatial resolution one way to reduce the over head is to read out the CCDs in binned mode There are other reasons some programs might want to bin their data during readout In this section we describe how you can switch the binning and provide some additional information on how the operational behavior of the observing system works when using binning 44 To set the binning in the ARCON console on rush or rust run setdet and be sure to exit setdet with Ctrl D IRAF Image Reduction and Analysis Facility PACKAGE astronomer TASK detpars gain 2 xsum 2 ysum 2 ysize 8192 width pixsize ES nxpixel 2048 nypixel 4096 detname Mosaicl mode ql Gain setting pixels summed in X direction pixels summed in Y direction Height of centered ROI full Pixel size in microns Detector size in X Detector size in Y Detector identification After exiting the setdet parameter file with Ctrl D you should get the following feedback If it does not appear most likely you have not successfully changed binning modes DEBUG Starting continuous DEBUG Starting continuous DEBUG Starting continuous DEBUG Starting cont
16. track The 2 TV guider filters are visible to the lower left and upper right of the science filter An Arcon controller can be seen in the background to the right 3 7 Operation of the Guider TVs Guiding with the Mosaic is accomplished using one of two TV cameras on the north and south sides of the science field These are intensified fiber optically coupled CCD cameras ICCDs and so they can be damaged if exposed to bright light The video signal from the selected TV camera is fed to the guider system The field of view of each camera is about 2 2 arcmin on a side at the 4 m and about 5 arcmin on a side at the 0 9 m The field of view of the TVs is fixed with respect to the science field At the 4 m the fields are approximately 1440 arcsec north and south of the center of the science field At the 0 9 m the fields are approximately 2400 arcsec north and south of the center of the science field TV focus can be moved remotely offsets are 0 9 and 1 7 at the 4 m and 0 1 and 1 9 at the 0 9 m for the north and south TVs respectively At a given location suitable guide stars are almost always available without moving the telescope from the desired position We find that we can guide at the 4 m on stars as faint as V 20 in full moon and at the 0 9 m to V 17 near full moon The TVs and guider are controlled by the telescope operator at the 4 m but by the observer at the 0 9 meter The observer needs to first select the N or S TV on
17. under the IRAF MSCRED package Before you get started you should be aware that the Mosaic multi extension FITS data format means that you will have to be careful to stick to the routines in MSCRED that can handle this format In many cases useful routines from CCDRED have been rewritten with the same name to be available in the MSCRED package IRAF routines in other packages can be used on one CCD at a time either in scripts or the command line but will not work directly on an entire mosaic image at once There is an MSCCMD routine that acts as an interpreter allowing you to use traditional IRAF routines on the Mosaic files if you need to use additional IRAF routines One of the first things that youre likely to do is to stack sequences of zero dark and flat exposures to produce superimages to feed into CCDPROC On the assumption that the darks and zeros are all the same using ZEROCOMBINE and DARKCOMBINE presents no complications On the other hand you are likely to want to scale the flats by their modes and this at present can be tricky Because of the importance of image defects modes and other statistics can be biased by bad values Normally a bad pixel mask will be available in the Mosaic database to improve the situation If you are after the ultimate in flat fielding you can 1 estimate the mode in two passes where the first pass restricted the range of allowable pixel intensities to plausible values and 2 the second pass used
18. which parameters are prompted for according to picture type While we were having trouble taking bias sequences at the KP4m during 2002 2003 they are working again Please feel free to take sequences of exposures without fear of hanging the system At the W0 9m there is still a problem Please use the script biases9 cl to take a sequence of biases 37 4 10 2 Getting more of the same Another useful command is e more Take one or more exposures exactly like the previous one The more command is slightly unusual in the way it prompts for parameters it is patterned after commands like directory and help If you type cl gt more you will not be prompted for the number of exposures as one might expect but rather a single exposure will be taken which more often than not is what you actually wanted to do Conversely cl gt more 10 will take ten more exposures 4 10 3 Taking a test exposure The test command is just like observe except that instead of creating a new image it always writes to an image called test fits overwriting any earlier version This can be useful e g for checking you have the field centered correctly If you change your mind and decide you want to keep the data just rename the image test fits 4 10 4 Taking your flats the easy way It s the end of the night You have taken data through a bunch of different filters Now you need to get flats for them all And all you really want to do is go to sleep
19. 0 100 74 5 81 8 40 Many mosdither options have now been used Feel free to contact us for more advice on setting up your own custom pattern e mosgrid is similar except that it takes images on a regularly spaced grid The grid is specified by the starting offset spacing and number of positions in RA and Dec again these may be given in arcseconds or in pixels cl gt lpar mosgrid exposure 60 Exposure time title Tr7 I grid Title for pictures npics 1 Number of exposures at each position xstart 0 initial offset in RA from current position xstep 20 step size in RA xsteps 20 Number of steps in RA ystart 0 initial offset in Dec from current position ystep 20 step size in Dec ysteps 2 Number of steps in Dec units pixels units of offset gohome yes return to starting position at end of grid guider_contr none Guider control mode resume no resume at next position in grid after quitting position_num 4 starting position in grid mode ql cl gt mosgrid Exposure time 0 60 Title for pictures Tr7 I grid Filter in wheel one I Telescope focus 3000 6000 4440 Filterl I Telfocus 4440 00000 Image obj031 Mosaicl 1 8315 1 8220 bin 1 1 gain 1 Observation finished Hit any key when ready guider working etc gt Observation finished All exposures finished Both mosdither and mosgrid include several important user options as h
20. 4m and rust at the 0 9m For more information on VNC see http www realvnc com 26 will not affect the operation of rush but should not be done when you are reading out an exposure or you will lose that exposure 3 Inthe VNC viewer window on tan or emerald click in the background of the display and select Re START ARCONS This should bring up all of the MOSAIC GUI controlled by rush rust This process takes about 2 minutes and you must also answer one question A small window labeled ARCON Console will appear near the left center of the screen in which various messages will scroll by After a few seconds a larger window labeled ARCON Acquisition will open immediately below this this is the window you will use for entering all data acquisition commands A brief greeting message will appear in this window and eventually you should be asked Do you want to synchronize parameters yes When you reply yes or just hit cr the detector parameters loaded into Arcon will match those stored in detpars and the positions of the motors recorded in instrpars will correspond to reality We currently recommend saying yes at the start of an observing run but no during subsequent restarts This saves slightly on the start up time In either case the IRAF package menus will be printed and the cl gt prompt will appear Some further windows will also pop up at this point The system is now ready for you to begin observing Occasio
21. 63031 Change the non zero numbers for each of the 4 lines and restart the Arcons The next time the Arcons are started the automatic CCD voltage calibrations will begin with these approximate values and should take less time to process 10 6 The ADC does not seem to be reacting fast enough The ADC GUI does not respond instantaneously to the motion of the ADC prisms There is a time delay If you restart ARCONS the GUI will occasionally not 66 even show the normal positions of the prisms but as soon as you turn on either of the non null modes and or move the telescope the display will update Similarly you might start an exposure and hear the shutter open before you see the ADC GUI update the positions of the prisms Be assured the prisms are moved before the shutter opens it is just the updating of the GUI that is lower priority for the CPU of rush rust 10 7 Warning message Warning ared package not defined when starting ARCONS When I start up ARCONS I see a warning message Warning ared package not defined do I need to worry about this No you can ignore this warning 67 11 Appendix F Rarely Encountered Problems Below are problems that have been seen in the past but rarely occur these days if at all 11 1 Good Error Messages Despite considerable detective work a number of error messages appear during the course of system startup that are completely benign and can be ignored At this time o
22. 83 and 98 C The dewar tank is cooled to 166 C or cooler A good way to detect the exhaustion of LN2 is the warming of the fill neck temperature which is normally near 0 C If this temperature begins to rise much above zero or any of the temperature boxes turn and stay red call for assistance to have the dewar filled Mosaic automatically e mails mountain personnel if various temperatures rise to levels that indicate a warm up Figure 3 2 1 The Mosaic system mounted at the back of the 0 9 m telescope The dewar containing the 8 CCDs is the silvery cylindrical object in the middle It is surrounded by the filter track which is housed in the large black oval that extends horizontally across most of the picture 3 3 The Arcon Controllers The eight CCDs are read out through four Arcon controllers These controllers run at 100 kpix sec per CCD yielding a readout time including all overheads of 2min34sec for Mosaic 1 only a single amplifier is used Data values are stored as 16 bit unsigned integers For further details about the Arcon controller systems see the technical paper by Roger Smith http www ctio noao edu instruments arcon arcon html The data taking computer rush or rust is a 125 Mhz Sun Sparcstation 10 running SunOS It has sufficient resources to manage the data acquisition but not 12 much more The large data volume is handed off to the reduction computer tan KP4m or emerald W0 9m via Fast Ethern
23. A computer is busy with othere tasks the display process cannot keep up and falls behind When taking short exposures of this type we suggest turning off the autodisplay option on the DCA GUI panel The current default is for the DCA to kill the previously running display process 69
24. Dispersion Corrector at the 4 m only PE EA E E 23 A SOORT O ririri ENA EAEE OLEE EESE EEEE EEVEE EAEE EE SEERNE 26 4 1 Logeing in and firing up the Arcon Mosaic Softwa isasisivcsssscsessansinssraannvearincierorarearonninniens 26 4D Atolo CRANE cerniere sever idan wherein waa eran ere ea Hiei 28 Ah NS Te ihe A SONATE eeo E AEE EEEE E 28 4 4 Restart and Power Cycling of the Arcons and Nexus Tram boX se sss ssssssrsrresnsrsresresnerse 28 4 5 Shutting down the sottware and Logging CUE ssesceniassnsanieasnsaiversnonsrscnsweniasanwapnhannsabiedsponansentes 33 4 6 OBSINIT rrise EEE E E E wma ais Lema ee 4 7 Re starting the MSE and related software esssss ssssssvssissistisstestinsinsiistisetiesiessistiette 34 4 8 Observe The Only Command You Really Need t KNOW issscssnsseiessunensearsnsiesnrsanasasianenacn 35 2 9 Exposure Control Commande sassari aiea ai einean AAEE RR IR E REG 37 L Oher Commands For Takte IRA ac ssncindsaceniestionxioadecieincanschaenleiaiiaioncnmerndnabonntnllontes 37 RSL Pa ea a a E E A E E A E 37 4 10 2 Getting more of the same ee ee er ee re eet 38 AN Dek NS OAR OR oon inane aca a AR ameneIES 38 410 4 Taking your flats We cast WY icinsicanniamianidnniatumiiainiadia aR 38 BTN Ma PRIS AM CONTIG sac acdenicsncca Sata snenth T tnbannentaes acsuniontersadeaten 39 4 11 Controlling the Data Capture Agent DCA on Tan or Emerald ccceceseeeceseseneseseseees 42 4 12 Observing in Binmed Mode scssminpsnasaeun neii hiu
25. NOAO CCD MOSAIC IMAGER USER MANUAL KPNO Mosaic 1 Specific System Version 3 0 September 1 2004 Revision by Heidi Schweiker and Buell T Jannuzi of the September 15 2000 version written by George Jacoby With contributions from Taft Armandroff Todd Boroson Jim De Veny Steve Heathcote Tod Lauer Bob Marshall Phil Massey Rich Reed Frank Valdes David Vaughnn The Veil Nebula courtesy Travis Rector Univ of Alaska Anchorage as observed with the WIYN 0 9 m telescope and Mosaic 1 send comments on manual to jannuzi noao edu or heidis noao edu Table of Contents L Mossie Orero Ar Leost koad THis ensinan n Moe ame 4 2 Torodd utt Ossis a EE AR E naa ede nas eA A aacoracee l nstiimernt Overyig Wasin iaaea uN e ieia EEA AEREA E KASATA RAN EASRA ERENER 8 2 2 Philosophy and Structure of Manual E E E T EO 2 3 Supplemental Information Other manuals and Web pages tO LOOK attesssssssessesssnssssteetsn g a E Noea EAEE sarne E E N EA EN malnueuncin es yees 10 zL The Mosale CC DSrreroroncrei rimi arn R E Re I2 The Powar nico dep eed ine ei R A 12 Ta The Aron Conme ecer E Le 2A The CCD Shute feonsoone nenna nn N 13 ao The Pier UW ste acer ccssaesu belek asa 14 30 Rihters For eNO BG ci ack acerca antenna sen iaotaeair eames Gans aed ivr E comedians 14 0 7 Operation Of the Guider TVS cnsicnasaniocraminincmmna ioc ienncenimanamnaiey 19 E OEO epn ener mre roar ernment Ty errr ete errr er ere reer tate ean E E 21 3 9 Atmospheric
26. already adjusted if inappropriately for the different pixel sizes so MSCIMAGE would then do no further adjustment Stars would be too bright in the corners of the flattened images but after re gridding their total fluxes would be scaled down to the appropriate values If the Mosaic images are to be analyzed individually however as might be done for standard star fields then after the flat field reductions are complete the differential scale effects must be restored The correction process is simple the scale at any point in the Mosaic field is already known from the astrometry so one could just calculate and multiply by a correction surface The final image would appear to have a variable sky level but would be photometrically uniform We also note that performing surface photometry on Mosaic images with their native sampling can cause biased results unless care is taken to track the changes in the pixel scale 5 9 Stacking Mosaic Images In many ways the real work of reducing Mosaic data comes when preparing to stack the images to make a final deep image free from gaps and artifacts Not only is there a premium on having well flattened data to begin with but one must also understand the relative photometric and sky level variations among the images in a dither set At any point in the final stacked image different frames will be making differing contributions Any differences in scaling will produce noticeable artifacts in the final sk
27. and filter is based on the same formulation as our 4 filter set liquid CuSO UG 1 Because containment of the liquid requires a thickness around the edge that exceeds the nominal Mosaic dead zone some vignetting is present At the 4 m the vignetting introduces a 20 loss of light at the edge but recovers to zero loss at 200 pixels from the edge 100 90 80 Transmission 3000 4000 5000 6000 7000 8000 9000 10000 Wavelength A Figure 3 6 1 The broad band filter set including the White filter 16 Transmission 10 3000 4000 5000 6000 7000 8000 93000 10000 Wavelength A Figure 3 6 2 The SDSS g r I and z filters along with Washington C and M M is the smooth curve slightly redder than g i jr oo p e E 3 E Transmission E 8 8 8 amp 8B g z i F Fi Penn ened Pema FF ame Figure 3 6 3 The current set of H plus redshifted filters Note that H 16 serves as a SII filter 17 Transmssion Transmission 4550 4600 4050 4700 4750 4800 4850 Wavelength A Figure 3 6 4 The blue Wolf Rayet filters for CINI He II and a continuum at 4750 100 30 80 70 60 50 40 30 20 10 4900 5000 5100 5200 5300 5400 5500 Wavelength A Figure 3 6 5 The ONI on band and off band filters plus DDO 51 18 4 V band Science Filter WA TY Filter TY Filter Figure 3 6 6 The V band filter installed in the filter
28. ange the exposure which may be positive or negative If used during a sequence the duration of the present exposure and all subsequent exposures is changed e stop Stop the exposure early read out the CCD and save the data to disk If used during a sequence the sequence is also terminated e abort Abort the exposure The CCD is not read out and any data collected during the exposure is irrevocably lost If used during a sequence the sequence is also terminated Do not abort a PAUSEd exposure resume first or suffer serious consequences i e results in a hung system which will need a restart e pictitle If when entering the title you typed M31 when you meant M33 you can use this command to give your image a new title 4 10 Other Commands For Taking Data 4 10 1 Taking exposures of specified type In addition to observe there are specific commands to take one or more pictures of each type e dark Take one or more exposures of type dark e dflat Take one or more exposures of type dome flat e object Take one or more exposures of type object e sflat Take one or more exposures of type sky flat e zero Take one or more exposures of type bias Except of course for the exposure type these commands take the same parameters and prompt for them in the same order as does observe Apart from saving you entering that one extra parameter use of these commands allows one to set default parameter values and also select
29. aring stars among the dither set Or you can specify a relatively representative image section and have MSCSTACK compute the modes The final stacking of the image by MSCSTACK can be done with any of the standard combining algorithms within the IRAF combine tasks Some of us prefer to use an average value with sigma rejection we also make complete use of the bad pixel map at this stage to eliminate known defects One might be tempted to use a simple median but in the limiting case of a large number of images this will only yield 80 of the signal to noise available from an average On the assumption that most vectors of pixels to be stacked will be valid an average with occasional rejection gives the best answer Going all the way through to this stage has produced final stacked images of variable quality depending on the conditions of the observation In non photometric conditions the sky may not be flat further scattered light from nearby objects may affect the sky over large areas unfortunately the pattern of scattered light varies as the telescope is dithered A further complication is that computation of an average mode for an image may be affected by scattered light that affects only a small 57 portion of the Mosaic field At this time we are still working on a solution for stacking images of this type the solution is likely to require fitting and subtracting a sky surface to the individual Mosaic images prior to feeding them to
30. c format as well as reduction and analysis tasks specific to Mosaic we have developed a set of IRAF routines available under the MSCRED package Almost all of the software tasks that we discuss below presume that you will be working within this environment A key factor that drives both the data taking and reduction of Mosaic images is the presumption that the final astronomical exposure will be built from a number of Mosaic images obtained by dithering the telescope This places strong demands on the quality of the data reduction to ensure the uniformity of the photometric response of the reduced image 5 1 Working with Mosaic Data Files An excellent summary of the Mosaic reduction routines is provided in the two guides written by Frank Valdes Mosaic Data Reduction System http iraf noao edu projects ccdmosaic Reductions and Guide to the NOAO Mosaic Data Handling System http www noao edu noao meetings spie98 mdhs ps We encourage Mosaic users 47 to read through these documents before attempting to reduce their data The guides also provide a thorough description of all MSCRED tasks that may be valuable during the night s observing The NOAO Mosaic data format produced by the Data Capture Agent DCA is a multi extension FITS MEF file The file contains nine FITS header and data units HDU The first HDU called the primary or global header unit contains only header information which is common to all the CCD images The re
31. common to all the extensions Thus one of the following commands will be sufficient to get header information about an exposure or set of exposures cl gt imhead obj 1 l Title listing cl gt imhead obj123 1 1 page Paged long listing cl gt hselect obj 1 Lfilter exptime obstime yes If you need to list header information from all the extensions then you need to take the additional step of creating an file For example to get the default read noise and gain values for each CCD cl gt imextensions obj123 gt list123 cl gt hselect list123 I rdnoise gain yes Rather than create an list you can use MSCCMD cl gt msccmd hselect input Lrdnoise gain yes The CCDLIST task in the MSCRED package is specialized for the Mosaic data It provides a compact description of the name title pixel type filter amplifier and processing flags By default it lists all the extensions but the extname parameter may be used to select a particular extension Because all extensions should 51 generally be at the same state of reduction it may be desirable to list only the first extension Like most of the CCD reduction tasks you can also select only a certain type of exposure for listing Examples of the two modes are Summary for all exposures cl gt ccdlist fits extname im1 Summary for all object exposures cl gt ccdlist fits extname im1 ccdtype object List of all extensions cl gt ccdlist obj123 5 4 Rec
32. d Remember that you will need to take bias frames and flats in binned mode to go with your binned science frames One can also block average the images MSCBLKAVG after readout if data volume is the real issue 46 5 Evaluating Recording and Reducing Mosaic Images In this section we discuss the software and observing procedures needed for the following 1 How to evaluate the observations as they are obtained at the telescope including how to display Mosaic images how to evaluate the telescope focus and edit and examine the image headers We also discuss how to log the observations 2 How to read and write the data from to tape 3 Calibration observations that should be obtained at the telescope 4 How to reduce the images Observers familiar with CCD cameras and the IRAF reduction and analysis software will find the processing of Mosaic images to be similar to cameras of more modest size At the same time there are a number of important differences that we touch upon briefly here To start with Mosaic images are recorded in a special multi extension FITS format MEF In brief the Mosaic CCDs are saved as individual images grouped together as separate entities in a larger FITS file only at the end of the reduction are the CCDs assembled as a single large astronomical image Because of this special format most IRAF routines will not work directly on the full raw Mosaic files To provide for processing of the special Mosai
33. e exposures prompting for the exposure type doobs a script which takes flats objects for a list of filters mosdither takes typically 5 dithered images in a single filter to fill the gaps in array more take more exposures just like the last one test take a test exposure The output image test is overwritten each time object take one or more object exposures zero take one or more zero bias exposures dark take one or more dark exposures dflat take one or more dome flats sflat take one or more sky flats focus take a focus frame recover Seana data if possible following a crash of the DCA during readout Exposure Control Commands pause pause exposure e g clouds do not ABORT or STOP from within pause resume Resume a paused exposure then ABORT or STOP if necessary tchange increase or decrease the exposure time stop stop an exposure and sequence of exposures reading out the detector abort abort an exposure or sequence discarding the data pictitle Change the title of the picture Quick look and Taping Commands on Tan at KP4m or Emerald W0 9m Mscdisplay display an entire mosaic frame Mscexamine general tool for examining images Msewfits write mosaic frames to tape in multi extension FITS format Caution Tape your data as you go DLT 7000 250 images tape and Exabyte drives 35 images tape and DDS 4 DAT drives 145 images tape are available On nutmeg KP4m it takes the following times to write
34. e original grid the noise in the tangent plane image shows bands of coherent noise structure This will be reduced somewhat in the final stacked image given the spatial de coherence of the images in the dither set Choosing the sinc interpolator significantly reduces the coherence but takes several times longer to process and may introduce a characteristic ringing around bad pixels Lastly as noted above MSCIMAGE has the option to correct the flux in the re gridded pixels for the variable pixel scale Use of this option should only be invoked when this information is preserved in the flattened images to begin with The final step is to combine the re projected dither set images using MSCSTACK This is the stage where careful attention must be paid to variations in zero point and sky level among the images Even on photometric nights the sky level is likely to change over the course of the dither sequence You can use the image modes to track the sky level but again one must be careful that the mode is not biased by bad pixels and defects You can for example calculate the average sky level for a dither sequence and then gave MSCSTACK a file specifying additive offsets for each image about this average At this stage you should also account for any photometric variations among the images MSCSTACK can also accept a file of multiplicative offsets These might be based on an atmospheric extinction curve on photometric nights or determined by comp
35. each image that is common to all images In effect IMCOPY provides a fast method to shift all the final images to a common astrometric system using integer pixel shifts You may also use IMSHIFT to apply a fractional pixel shift but this introduces another interpolation that I have not found necessary 58 6 Appendix A Miscellaneous Software Commands Parameter Sets and Related Commands newpset unlearn specified parameter sets psets restoring default values General Parameters obspars parameter set pset containing general observation parameters picnum parameters of focus frames observer etc telpars parameter set containing telescope parameters not much though Detector Parameters detpars pset containing parameters of the detector binning detector download detector parameters from detpars to the controller setdet edit detpars and then execute the detector command do not use ccdinfo list parameters of detector and other interesting information kleenex guarantee that all the ex tasks e g muxnex have shut down Instrument Parameters instrpars pset containing instrument parameters filter telescope focus etc wheell pset containing filter names and related information motor move motors in the instrument or read current positions Includes motor move move motors prompting the user for the required positions motor go move motors to the positions specified in instrpars motor status l
36. eductions The Mosaic camera also has a spatially variable pixel scale that has important implications for ensuring a uniform photometric zeropoint in the reduced images 5 6 Calibration Data to Obtain At the Telescope Good data reduction begins with obtaining good calibration data at the telescope Dark frames may be required but usually not It is safe practice to obtain darks with exposures similar to your science images Dome flats provide basic flattening of the frames to 1 or so but night sky flats or illumination corrections likely are required to produce images that can be stacked without introducing obvious artifacts Using night sky flats we can flatten images to 0 1 twilight flats do not appear to work quite as well as dark sky flats due to regions of variable thinning that cause slightly wavelength dependent features but they work better than dome flats The default Mosaic dither pattern is a sequence of 5 exposures designed to insure at least 80 coverage for all portions of an astronomical image given the gaps between the CCDS Finally good astrometry is required to register and stack the Mosaic images We have derived solutions for most filters but the scale varies slightly with color so you may want to image an astrometric field if you are using your own filters Our experience indicates that the array is geometrically very stable 53 5 7 Basic Reductions Almost all of the basic image reduction is done
37. element correctors currently in use should exhibit a similar effect and tests performed by Alistair Walker with the CTIO 4 m confirm this analysis Although the ghost pupil can subjectively appear severe when viewed at high contrast for narrow band filters photometric accuracy is preserved when this additive term is removed during the reductions One can avoid the affected region on the Mosaic array by moving the telescope slightly if there is any concern about the reduction process see Sec 4 For a description of how to correct for pupil ghost images in your observations you can read the discussion in the NOAO Deep Wide Field Survey MOSAIC Reduction Cookbook http www noao edu noao noaodeep ReductionOpt frames html 3 9 Atmospheric Dispersion Corrector at the 4 m only The Earth s atmosphere disperses the light from stars significantly when observing away from zenith The effect is greatest and similar at U and B where the stellar image is stretched for example 0 5 at a zenith distance of 45 1 4 airmasses and 0 9 at 60 2 airmasses The ADC prisms can be configured via a rotation to counter this effect nearly completely thereby greatly reducing the elongation of the image introduced by the atmosphere Modes of Operations There are 3 modes that the ADC system can be used Null mode where the ADCs make no correction Track mode where corrections are periodically updated and Preset mode where the correcti
38. equence exposures you may use MSCEXAMINE or MSCFOCUS With the former you measure individual widths and keep track of the focus values yourself With MSCFOCUS which is a Mosaic version of KPNOFOCUS you mark the top exposure on any CCD for each star and the task measures all the exposures in the sequence and estimates the best focus value using 50 information recorded in the data file To run MSCFOCUS on a displayed exposure just give the command with a file name it will display the exposure if needed cl gt mscfocus To measure pixel statistics you may use MSCEXAMINE or MSCSTAT a Mosaic version of IMSTAT MSCSTAT runs IMSTAT or each of the selected extensions in a list of Mosaic files To restrict the measurement to a region you use image sections which apply to all of the selected extensions For example to measure Statistics at the center of a set of observations the command would be something like cl gt mscstat fits 900 1200 2000 2300 There was some discussion earlier concerning use of generic image tasks with the NOAO Mosaic data The tasks IMHEADER and HSELECT fall into this category The two important points to keep in mind are that you must specify either an extension name or the extension position and that the headers of an extension are the combination of the global header and the extension headers Often one does not need to list all the headers for all the extensions The image title and many keywords of interest are
39. et for all analysis and reductions thereby relieving rush rust of unnecessary loads These are fast Linux boxes with gt 100 Gbytes of disk and gt 1 Gbyte of RAM SS ee TY Camera South oom Figure 3 3 1 A view of the Mosaic system on the 0 9 m telescope indicating 2 of the 4 Arcon controllers Also the south guide TV housing can be seen as well as the Mosaic dewar now appearing in black 3 4 The CCD Shutter The shutter consists of a pair of opposing sliding blades one of which has rectangular slots open for the guide field The blades are attached to pneumatically driven cylinders to provide very fast control of the shutter This design allows the TV guide fields to be shuttered independently of the science field In the guide mode the closed shutter still allows the TV guide cameras to see the sky In the dark mode these fields are closed as well The acquisition software controls which mode the shutter remains in between exposures For object observations the shutter goes to the guide mode before the exposure begins For requested observation types of dark flat or zero the shutter goes to the dark mode before the exposure begins and remains in this mode after the exposure and readout are completed Note that the TV fields are always open when the shutter is open the different shutter modes only control the TV fields when the science shutter is closed If you have been taking darks flats or 13 zeros you may need to set t
40. ew parameter set too called mimpars which controls the on the fly processing You can select overscan correction flat field correction both or none MSCDISPLAY offers a special mode of display not previously available If invoked before the readout of the Mosaic array is complete MSCDISPLAY will begin painting the XIMTOOL screen with as much data as are available at that moment When automatic gray level scaling is used it will compute the scaling based on the amount of data present when it starts It will then keep the same scaling for 49 the number of display and sleep cycles given by the niterate parameter after which it will compute a new display scaling and reload all the currently recorded data Thus a small value for the niterate parameter will update the scaling frequently and a large value will update more infrequently The trade off is that calculating the scaling takes a significant amount of time and causes the whole display to be reloaded while using only the first scaling based on just a little bit of data may result in poor scaling values Generally we recommend infrequent updates because of the very lengthy time required to display an entire image This use of MSCDISPLAY is only sensible if automatic displaying is disabled from the DCA GUL The MSCDISPLAY task is automatically started when a new image is reading out The IRAF Data Capture Agent DCA controls this default behavior Whether to display or not is control
41. f the Nexus TRAM box in the computer room see figure 4 4 1 b Go to the instrument and power off the Arcons There are 4 red power switches located on a power plug strip see figure 4 4 2 Wait 10 seconds Power on the 4 Arcons c Complete step 4d by powering the TRAM box on d Log back into both computers to restart the Arcon and DCA software e If the system still fails to run try steps 1 3 several times If that fails call for help 31 Power Swi oar Nexus Tram Box a u Figure 4 4 1 The Arcon TRAM box with Power Switch noted At the KP4m you should not need to use this switch see section 10 2 Figure 4 4 2 The Arcon power strip with 4 power switches noted 32 4 5 Shutting down the software and Logging out During your run you may wish to stay logged in continuously to maintain your window environment especially if you ve taken some time to move and resize dozens of windows On the other hand some folks feel that a clean environment makes for healthier observing thus you may wish to log out at the end of every night to reset any gremlins back to their initial conditions In all cases after your last night you should log out completely from both rush rust and tan emerald To log out of tan or emerald it is not necessary to shutdown Arcons you can simply close the VNC window However one can first end the Arcon session on rush rust if desired e Onrush rust Move the
42. ftware which links everything together MPG router are normally started by support personnel when the instrument is installed on the telescope However a restart may be necessary from time to time If the MCCD temperature readouts then there may be a problem with this software rush rsh taupe at the 0 9 m or cinnamon at the 4 m taupe ps ax grep msmid is it there no taupe start msmid 34 4 8 Observe The Only Command You Really Need to Know All data taking can be done by using a single command observe This command takes one or more CCD exposures as in the following example cl gt observe Exposure type zero dark object comp pflat dflat sflat focus zero obj Number of exposures to take 1 1 Exposure time 0 0 300 Title of picture M33 V Filter in wheel one B V Telescope focus 0 10200 Filterl VTelfocus 10200 00000 Image obj022 Mosaicl 1 8315 1 8220 bin 1 1 gain 1 cl gt Observation finished You will be prompted for all the information required which includes e Exposure type can be zero sometimes referred to as bias dark object dflat sflat or focus Note that when selecting from a list of options like this you may enter any unique abbreviation Focus exposures which are somewhat special are described fully below in taking a focus frame e Number of exposures to take a sequence of this number of pictures all having the same parameters wi
43. he Arcons via the background menu Re Start Arcon Session f You may have to execute the level 3 commands to make any progress g At this point it probably wont hurt to restart the DCA on the data reduction computer using the pull down menu 5 This is the most serious mode and it should be done with the cognizance of NOAO personnel This will be a total restart of the system Follow the process in item 4 above for the data taking computer but only through step c Then quit the DCA on tan or emerald AT THE 4 M it is possible to cycle power to the instrument and Nexus Tram box remotely a From a UNIX prompt type telnet 4m nexus power Use 4meter as the username The password is posted in the control room To turn off the power to the Nexus TRAM box type off 1 at the prompt and confirm with Yes 30 b From another UNIX prompt type telnet 4m pf power Use 4meter as the username The password is posted in the control room To turn off the ARCON power controller type off 1 at the prompt and confirm with Yes c Slowly count to 50 d Turn on the ARCON power controller by typing on 1 at the prompt in the 4m pf power window e Turn on the Nexus box by typing on 1 at the prompt in the 4m nexus power window f If the system still fails to run try steps 1 3 several times If that fails call for help AT THE 0 9 M you will need to bring the telescope to zenith and cycle the power on the instrument manually a Power of
44. he pixels is done so that the shift and stack step does not require any further re sampling Up to this point the individual CCD images are each stored in their own partition in the multi extensions FITS files MSCIMAGE pastes the individual CCDs into a large single FITS image accounting for their accurate relative positions and rotations given the astrometric description of the field MSCIMAGE further re grids the pixels into a tangent plane projection which yields pixels of essentially constant angular size over the extent of the Mosaic field This is also the best point to fold in knowledge of the bad pixel map The bad pixel map itself can be re gridded by MSCIMAGE giving the final routine MSCSTACK complete knowledge of where the bad pixels are If the bad pixels had been replaced prior to this point and had not been flagged in the Mosaic images themselves their locations would have been unavailable in the final stacking 56 Some of us prefer to clear out the bad pixels right at the beginning of the CCDPROC process Re gridding the Mosaic images requires a method to calculate new pixels interpolated from the original ones One can select from any number of the standard IRAF interpolation routines however given the immense quantity of the data involved we have always selected bilinear interpolation for speed considerations Unfortunately bilinear interpolation smoothes the noise slightly and as the new pixel grid beats against th
45. he shutter mode to guide in order to get light to the TV guide camera The time for the blades to move completely across the field is 23 msec The motion of the blades during both opening and closing are in the same direction so that the exposure level is nearly constant over the array The motion of the shutter blades is along columns The accuracy of the shutter has been measured to be 3 in a l second exposure that is the exposure is really 0 97 seconds see also Section 8 3 5 The Filter Track The filter track holds 14 filters For each filter position there is a filter for the CCD field and two separate filters for the two TV fields Separate filters are used so that a narrow bandpass science filter does not constrain the observer to find very bright guide stars Normally one would use clear BK7 filters for the TV but one can use a red filter to minimize moonlight or match the science filter more accurately One might want to match the science filter at least approximately to minimize a guider drift Even at the 4 m residuals after the correction from the ADC are of order 0 1 0 2 arcsec This and all filter decisions must be made ahead of time as the filters can only be changed during the day by a qualified observing technician Adapters exist to allow the use of 4 inch square 1 adaptor and 2 inch square 2 adaptors At the 0 9 m f 7 5 these 4 inch filters illuminate approximately 6K X 6K pixels 56 of the total sky area
46. his name is derived from the exposure type by appending a running number which is automatically incremented after each exposure how this number can be adjusted and alternate naming schemes are described in obspars The image will be created in the current directory at the time the observe command was issued The observe command terminates as soon as the exposure starts and you can enter other commands in the IRAF acquisition window While you could type any IRAF command you like we suggest you keep this window free for entering the special exposure control commands The status window will keep you informed of the progress of your exposure As soon as the exposure starts the first line will change from CONTINUOUSLY_ERASING to INTEGRATING and the status window will also show parameters of the exposure such as the picture title A counter in the status window and more legibly the countdown window will begin counting down the time remaining in the exposure Another counter will count up the dark time the time since the CCD stopped being erased This will be slightly greater than the elapsed exposure time due to overheads in the controller and will of course be very much longer if you paused the exposure When the exposure finishes the CCD will be read out The first line in the status window will change to READING and the buffers read counter will indicate the number of buffers of data successfully transferred to the Sun The data
47. ic 2 has similar cross talk between amplifiers but in a more complex matching due to the 16 amp readout For both instruments these echoes can be effectively removed with the CCDPROC xtalkcor option turned on While the magnitude of the cross talk is generally stable it does change on relatively long time scales We have a library of past xtalk coefficients used for the correction process available in IRAF in mscdb and at http www noao edu noao mosaic mosaic calibs html It is possible to calculate your own set of new coefficients from your own data using the xtcoeff task in the mscred package of IRAF One can also adjust the provided files slightly and reprocess checking the residuals until they are smaller than the noise in the image A more complete discussion of how to determine your own coefficients will be included in a 64 future update or you may contact Buell Jannuzi at jannuzi noao edu for more information Figure 10 3 1 A sample echo appearing in CCD 3 from a saturated star in CCD 4 10 4 Bad Rows in All CCDs We are occasionally seeing images in which one or more bad rows appear in all the CCDs An example is shown below in Figure 10 4 1 The cause is unknown but common to both Mosaic systems KPNO and CTIO Not much can be done with the images to fix them but a subsequent median say from a dithered sequence ought to reject outlying pixels Figure 10 4 1 A region of a mosaic image from CCDS 3 and 4 botto
48. ictures really end up on a faster computer known as emerald at the W0 9 m and tan at the KP4 m where you can display and examine the data perform full reductions and tape the data much more effectively Rush and Rust should be used only to do the minimal work required to take observations because the data rate through it is tremendous and nearly pegs the CPU at 100 Pictures are 135 Mbytes each A typical night of 70 pictures produces about 10 Gbytes Be aware that processing this data even just reading it is a major task for many computing systems We recommend using a DDS 4 or DLT tape however we provide Exabyte 820 8505XL compatible drives for those who do not have DDS 4s or DLTs Provide enough time to tape your data each night With the Exabytes an image takes 1min20sec to tape using tan so 70 pictures will take nearly 2 hours even without a verification pass We also offer DDS 4 DAT DVD and CD RW at both telescopes The Mosaic cameras require large 5 75 inch filters to avoid vignetting We can provide an adapter for 4 inch filters but using them makes poor use of the Mosaic s wide field 2 2 Philosophy and Structure of Manual This manual was originally intended for an observer planning to use either of the NOAO CCD Mosaic imagers It is not intended to serve as a hardware or software reference document describing the inner working of the Mosaics although some details at that level are present to help the observer plan
49. idden parameters First there is guider_control which can be set to none if you are not using the guider at all wait which waits for the observer to do whatever they wish to do before starting the next exposure and onoff which should be used most often when you are using the guider In the onoff mode the guider is turned off the telescope is moved by the proper dither grid motion and you are prompted to hit any key when the guider has been readjusted for the motion of the telescope guide star when you hit a key the guider control is automatically restarted 41 In addition position_num provides control to pick up in the middle of a dither grid sequence should a crash occur before the sequence was completed 4 11 Controlling the Data Capture Agent DCA on Tan or Emerald A screen capture of the current set of graphical user interface GUI control windows that control data acquisition and post processing on tan emerald is shown below Most operations should be self explanatory but for that rare button that defies interpretation the on line help button should clarify the situation caa Console monitor III OS File Edit Options Help dui CA Console Honitor Inage Directory nd2 dneter Sept032004 Inage Type dark Inage Filename dark028 fits Filter Nane R Harris ki004 Hdr Pkts Pix Pkts EI Readout Status Options Display Enable Postproc Enable J fAuto Kill Enable Done Disk Usage 30 E
50. in the event that the coordinate origin is lost or corrupted as happened a few times in our reductions The MSCZERO routine uses the known astrometric description of the Mosaic field so that the location of any star identified can be used to set a global origin In passing we note that the quality of the astrometric solution is excellent stars can be located to a fraction of a pixel 0 26 at the 4 m in all portions of the field MSCCMATCH uses the astrometric solution and recorded relative telescope offsets to locate the registration stars in a given image it can also be assisted by running the images through MSCZERO if this assumption fails for some reason Once a given star is located it is cross correlated with the same star in the fiducial image to calculate a positional offset You have the option to review the quality of the match to decide if it is acceptable The final offset is the average of the individual offsets with a check for outliers This interactive approach gives the best confidence that the correct offsets are being used but the entire process can be run in an automated fashion Also MSCCMATCH can access a position catalog and interactively display the known stars on the Mosaic image to provide a totally independent solution for each dithered frame The penultimate step in stacking Mosaic images is to re grid them into common tangent plane projections using MSCIMAGE The use of a common projection aligned to the centers of t
51. inuous In the example above we have set the xsum and ysum parameters To switch back erase erase erase erase binning mode to 2 by 2 by adjusting the to unbinned mode run setdet again and reset these parameters Do not adjust the GAIN mode After running setdet subsequent exposures should appear in the desired mode Check your first exposure to make sure it is the format you desire We have occasionally seen the setdet task fail to reset the mode Normally just running the task again will succeed in adjusting the mode but occasionally you will have to restart the ARCONS and try setdet again Please note that several features of the MOSAIC system do not currently work as well when observing in binned mode These include the following e The display processing controlled by the DCA applying the on the fly flat and over scan bias correction does not work as well We suggest you turn off this feature The mscexamine which can normally be used to display object shapes and intensities of portions of the image even while the image is being readout will not work properly Images of objects which are round will appear pixelated when the e contour plot and other options are used 45 e The cores of bright saturated stars are not handled properly and will be negative These will appear as white holes in the centers of these stars when the image is displayed Photometry of the other objects lower counts is not affecte
52. ist current positions of motors motor enable disable enable movement of individual motors motor init instrument connect initialize filter wheel names ICE like synonym for motor move Additional Commands for support staff establish the connection between the IRAF UI and 59 disconnect reconnect send pconv arsh mux fhdr shutter gwcopen gwcclose gwcsend mseshutter mailtemps off mailtemps on mailtemps status savewheell Arcon controller break the connection between the IRAF UI and Arcon controller break and re establish the connection between IRAF and Arcon a command to the detector controller Arcon send a command to picread picfeed send a command to arsh clarsh send a command to muxnex send command to fitsheader server Command Arcon to open close the shutter establish the connection between IRAF and the instrument break the connection between IRAF and the instrument send a command to the instrument controller Command the instrument controller to open close the shutter and set the shutter ready position disable temperature warning emails enable temperature warning emails reports whether the temperature warning emails will be sent on or not off ove into an xterm window this saves the current filter 1st 60 7 Appendix B Differential Refraction With the wide field of the Mosaic imager one should be aware of the special conditions imposed by differential atmospheric refraction during expos
53. ldcard notation for specifying a set of extensions So to apply an arbitrary IRAF command that takes a list of images you must either prepare an list or type the list explicitly or use the special MSCCMD command The task MSCCMD takes an IRAF command with the image list parameter replaced by the special string input The input list of Mosaic files will then be expanded to a list of image extensions Section 4 3 illustrates the use of MSCCMD with the HSELECT task 5 2 Displaying and Evaluating Images at the Telescope During observing a small set of IRAF commands are commonly used to examine the data This section describes these common commands While this 48 section is oriented to examining the data at the telescope during the course of observing the tools described here would also be used when later reducing data The two commands DISPLAY and MSCDISPLAY are used to display the images in XIMTOOL The DISPLAY task is used to display individual images in this context the individual CCDs in a Mosaic exposure There are many display options that are discussed in the help page The only special factor in using this task with the Mosaic data is that you must specify which image to display using the image extension syntax discussed previously As an example to display the central portion of extension im3 i e CCD 3 in the first frame and the whole image in the second frame cl gt display obj123 3 1 fill cl gt display obj123 3
54. led by the DCA user interface the DCA GUI see Sec 4 9 5 3 Examining the Data Once you have displayed the Mosaic exposure you will need a few more commands specific to Mosaic to interact with the display to do such things as looking at exposure levels checking the focus and so on Just as we have written MSCDISPLAY as a special version of DISPLAY we provide the MSCEXAMINE routine as an analog of the standard IMEXAMINE to allow for interactive examination of Mosaic images MSCEXAMINE is essentially the same as the standard IMEXAMINE task except that it translates the cursor position in a tiled mosaic display into the image coordinates of the appropriate extension image Line and column plots also piece together the extensions at the particular line or column of the mosaic display To enter the task after displaying an image the command is cl gt mscexam As with IMEXAMINE one may specify the Mosaic MEF filename to be examined and if it is not currently display it will be displayed using the current parameters of MSCDISPLAY To modify the radial plot parameters in MSCEXAMINE type cl gt rimexam2 which is analogous to rimexam for IMEXAMINE Or you can use the approved mechanism for modifying parameters within the 7EXAM tasks by typing g to switch the focus of the mouse cursor to the graphics window i gets you back to the image and typing e to edit the parameters of the sub task being execute For evaluating focus s
55. ll be taken e Exposure time the integration time in seconds which need not be an integer This parameter will not be requested in the case of exposures of type zero for which it is 0 0 by definition e Title of picture this will be included as the title in the image header In each parameter query you are supplied with a default value which you can accept by simply hitting CR these default values are just the previous entries If you make a mistake or change your mind you can abort the command during the parameter entry stage by typing ctrl c the superstitious may enter the command flpr at this point in order to ward off the evil eye For exposures of types other than zero and dark you may also be prompted for the following parameters of the instrument telescope e filter in wheel one the required filter Note that filters are specified by name rather than by their position in the filter wheel the way this translation is set up is described in wheel psets 35 e Telescope Focus the telescope focus setting You can control whether you will be prompted for these instrument related parameters during observations see section on motor control Once you have entered all the necessary information there will be a short pause while the motors in the instrument are moved to the required positions and then your CCD exposure will begin A short message will be printed which includes the name of the picture which will result T
56. m and 7 and 8 top showing a series of bad rows CCD 3 has a bad column down the middle The bad rows are about a quarter of the way from the bottom of CCDs 3 and 4 and a quarter of the way from the top of CCDs 7 and 8 65 10 5 Calibrating the CCD Voltages at the Start of a Block CAUTION The following procedure should only be performed by NOAO technical staff A typing error can easily leave the Mosaic system in an unusable state At the start of a run or if the ambient temperature has changed more than about 10 degrees C it is necessary to calibrate the Arcon boards If you don do this then subsequent Arcon restarts will be take an extra 5 minutes or so From the ARCON Console window type arsh gt all video calibrate input This may take up to 6 minutes Then type the following sequence arsh gt b1 video report arsh gt b2 video report arsh gt b3 video report arsh gt b4 video report The b numbers refer to the Arcon box numbers After each command review the line that starts with coarseinput 0 There are 4 numbers for which 2 will be exactly 0 when running in 8 channel mode The other 2 numbers should be around 3000 Now edit the file on RUSH called datal 4meter arshre or data1 36inch arshrc which near the bottom has a set of lines like b1 video calibrate input 3092307732053218 b2 video calibrate input 3085306230513208 b3 video calibrate input 3027311230343047 b4 video calibrate input 32643254304
57. m images are excellent across the entire 35 x35 field On good nights we have documented uniform 0 65 images in R There is no measurable focus gradient or PSF variation to within 10 The 0 9 m telescope is not as well corrected There is a small focus gradient across the 59 x59 field amounting to 20 30 focus units Images in the corners of the mosaic degrade somewhat especially in the lower left corner CCD 1 Also the corners of the field are slightly vignetted 5 10 by the internal telescope baffle Image Scale The 4 m scale is slightly variable 6 3 due to pincushion distortions from 0 261 per pixel at the center f 3 1 to 0 245 per pixel f 3 3 at the corner of the field The 0 9 m scale is 0 425 per pixel The spatial variation is small with the scale decreasing to 0 420 per pixel at the corner of the field 22 Ghost Pupil When using narrow band interference very blue e g U or red e g I z band filters at the 4 m a faint image of the telescope pupil falls on the CCD and has a diameter of about 10 arcmin Depending on the bandpass and construction of the filter this reflection typically manifests itself at lt 1 for broad band to 2 4 narrow band Om Ha U I z level above the background It arises from an internal reflection off the front surface of the rear element of the corrector despite the use of an extremely good anti reflection AR coating Our investigation suggests that similar 4
58. magnitudes for many objects Due to the wide field and multi CCD nature of Mosaic though there are several issues that may affect the accuracy of one s results and in particular the hope of achieving 1 photometry CCD to CCD sensitivity differences While flat fields remove the gross sensitivity differences across the CCDs each CCD exhibits its own spectral response Relative to the B band U sensitivity varies by up to 10 and V by 5 from CCD to CCD Consequently the color terms for one CCD are not applicable to data taken with another CCD At a minimum therefore one must know the color terms for each CCD But there is another quirk if data are taken in dithered mode then some stars may have been exposed across several different CCDs each with different spectral properties Photometry from the stacked image will be sensitive to the combination of color terms Variations in spectral characteristics on a single CCD even across a single CCD there are variations in sensitivity approaching 4 U relative to B This problem though is not new the old TI and Tektronix CCDs also exhibit variations almost as large Shutter corrections The large shutter for Mosaic is not perfectly accurate That is a command for a 1 second exposure will not open the shutter across the entire array for exactly 1 000 seconds As of November 2003 a 1 second exposure held the shutter open for 0 97 seconds at the top of the array and 0 96 seconds at the b
59. maining eight HDUs called extensions contain the images from the eight CCDs The fact that the image data are stored as FITS format images is not particularly significant A single FITS format image file may be treated in the same way as any other IRAF image format The significant feature is the multi image nature of the data format This means that commands that operate on images need to have the image or images within the file specified Only commands specifically intended to operate on MEF files such as those in the MSCRED package can be used by simply specifying the file name Commands that operate on files rather than images such as copying a file may be used on MEF files In general it is safest to use only MSCRED commands on MEF files IRAF V2 11 is required to run MSCRED As of September 1 2004 we are running IRAF V2 12 2a as well as MSCRED V4 8 on tan emerald and nutmeg The basic syntax for specifying an image in a MEF file to an IRAF task is filename extension where filename is the name of the file The fits extension does not need to be used The extension is the name of the image For the NOAO Mosaic data the eight CCD images have the names m1 through m8 but the simple through 8 works too The extension position in the file where the first extension is 1 may also be used To access the global header for listing or editing the extension number is 0 i e filename O There is currently no wi
60. n ponte eae ener 44 5 Evaluating Recording and Reducing Mosale DMiageS css scdansenicashzaeidnansetneniaseaciapnsennds sanankshsnsemuntaseasiaiansneasanesnen 47 51 Working with Mosale Data Files sissende cann inaen eara TEAS RaR RI 47 5 2 Displaying and Evaluating A at the itunes AEE diene A 48 5 3 Examining the Data ai E ee E E er we ne Recording Wiesel IDA vaccionumrcnmtene a R O EE 52 5 5 The Reduction o Mossie Tee caniin a NAT aR 53 6 0 Calibration Data to Obtain At the Telescope iiiwnaadiininndinneonnatnnnnndnnanawana 53 PB a Fer IIS oir EE E 54 5 8 The Variable Pinel Scale and Zero Point UmfOrmity acsisassassssassaricsnnanssvsaiamcncantanginsassarinaaranaionn 54 Ao Stacking Maka ImAge Sorser e Wao EE AE E EE 55 5 10 A Simplified Summary of the Processing Steps pai eee 6 Appendix A Miscellaneous Soltware Comins cscsacsscissasinenssncansieratantnaasancivrasasene SE rere te D9 nAppendix B Differeria ReMANO NEE AERE EESE 61 Pee ie Aboni THONE niece eee 9 Appendix DiE hield Exess e aed 10 Appendix E Frequent Encountered j Dianin s FEP E E E A E 11 Appendix F 1 Mosaic 1 Overview At Least Read This The Mosaic 1 and Mosaic 2 imagers are wide field optical imaging cameras built for use at Kitt Peak National Observatory and Cerro Tololo Inter American Observatory These two cameras are nearly identical but do differ in some respects The operation of each of these cameras Mosaic 1 at the KPNO
61. nally things will get hung up during the process of downloading and initializing the Arcon software If this happens you may see the message but probably not KKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKK k k FAILURE DURING ARCON STARTUP kx Use re start button to try again kx KKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKK In the majority of cases simply performing the restart procedure will fix this problem although it may be necessary to try this more than once If after repeated attempts the system will not start refer to the Frequently Encountered Problems section for further advice e Right click on the background of TAN 0 0 or Emerald 0 0 and select Re start DCA When you started ARCONS on rush rust the start up procedure will 27 have killed the previously started DCA You can restart the DCA right after you start the ARCONS on rush rust you do not need to wait until the ARCON start up has completed The system is now ready for you to start observing 4 2 Autologging If you would like to use electronic auto logging of your observations you will need to follow the instructions here http www noao edu kpno manuals aol including running loginit in a data reduction window on tan or emerald 4 3 Restarting the Arcon software Every so often something or other happens which causes the Arcon software to hang or otherwise get confused In the vast majority of cases this can be fixed by simply restarti
62. ng the software running on rush rust This takes only a couple of minutes e On rush rust inside the VNC window on tan 0 1 or emerald 0 1 Move the mouse pointer to an empty section of the desktop and hold down the right hand button to bring up the desktop menu Select the item End ARCON Session and release the mouse button After a few seconds the ARCON console Acquisition status and countdown windows will disappear Once the windows have successfully closed and the CPU meter has dropped to zero you can then restart the Arcon Session Again bring up the desktop menu via the right hand mouse button and select Re Start ARCON session The software will go through the startup procedure described in 4 1 You should normally answer yes to do you want to synchronize parameters This ensures that the detector parameters and filter positions etc match those in use prior to the re start Any other windows on the desk top will be untouched so any processes running in them will be unaffected and you can continue to work in these windows When you Re Start Arcons the DCA on tan or emerald will close You will need to restart it again To do this hold down the right hand button to bring up the desktop menu and select Re Start DCA and release the mouse button 4 4 Restart and Power Cycling of the Arcons and Nexus Tram box Occasionally the Arcon controllers get into a weird state There are roughly 5 levels of severity with which the use
63. nly one such error survives a ERROR Unsolicited data or missing data address During an Arcon restart you will always see 6 8 messages by WARNING Command timed out waiting for sub command This can sometimes be benign and sometimes serious It often shows up at the end of a sequence of exposures c ERROR Still processing last command please WaitForDone This has also been seen at the end of a sequence with no serious consequences 11 2 New Errors as of September 2000 With the upgraded video processor boards installed during the summer of 2000 several new error messages are available for you to ponder Generally these are bad messages meaning that you have to restart the Arcons to take pictures But of course you should try to ignore them first The Index too small error is bad It usually occurs during an Arcon start Often a few more startup attempts will clear the path to success ERROR Index too small Calibrate The SEVERE ERROR shown below is just one of a few dozen that will appear at once These mean that the CCD has been powered down by the Arcon thinking that the AC power is suspect You will not be able to take a picture and an Arcon restart will be needed Check with someone though about that suspect AC power SEVERE ERROR B4 Testpoint 3 LG1 reading 14 96 is under absolute limit 6 000000 68 11 3 Image display fails to complete automatically If the data rate is fast and the DC
64. ntial refraction between the guider and the science CCDs will change as a function of telescope position and will cause blurring for long exposures at high zenith distances if the ADC is set to Null Mode In this case the observer should select an ADC Filter Mode that encompasses both the narrow band filter and the TV camera filter bandpasses and select ADC mode 2 or 3 track or preset The ADC GUI Control of the ADC prisms and modes is selected via the ADC GUI see Figure 3 9 1 Status of the ADC prisms also is displayed in the GUI window The primary user parameters in the GUI that concern the observer are the ADC Mode Null Track Preset and ADC Filter Mode U B V R D pee ADC Configuration Filter Mode J filter verification prompts R filter Help View log H Observing Mode w E x Mul Preset Track i60 hike 0 04 ra ae a 2 359 94 V Re index Oc Last ADC adjustment occurred at 14 36 53 MST Last re index at 16 33 35 Sep 1 Key Click to minimize window RA 0 14 27 59 DEC 16 23 38 7 Telescope azimuth 123 18 Zenith angle 72 38 Filter R Harris k1004 Moving ADC to optimal position please wait Figure 3 9 1 The ADC GUI When you change the filter you are using with the ADC in use you will be prompted to confirm that you want to change the operating mode of the ADC There is no beep or other sound warning that the system is waiting for your confirmation There is a pop up windo
65. o edu kpno mosaic mosaic html NOAO CTIO Mosaic Web Pages http www noao edu ctio mosaic WIYN 0 9 m User s Manual http www noao edu 0 9m manual html Buell Jannuzi s Reduction Guide http www noao edu noao noaodeep ReductionOpt frames html Various Publications SPIE ADASS Mosaic Data Handling System Valdes 1998 SPIE 3355 497 http www noao edu noao meetings spie98 mdhs ps CCD Detector upgrade for NOAO s 8192 x 8192 Mosaic Wolfe 1998 SPIE 3355 487 http www noao edu noao meetings spie98 wolfe html What is better than an 8K x 8K Mosaic Muller 1998 SPIE 3355 577 http www noao edu noao meetings spie98 muller ps A New Wide Field Corrector for the Kitt Peak Mayall 4 m Jacoby 1998 SPIE 3355 721 http www noao edu noao meetings spie98 jacoby ps 3 The Mosaic Hardware 3 1 The Mosaic CCDs The Mosaic Imager features eight 2048 serial or pixels row x 4096 parallel or pixels column 15 um pixel CCDs arranged as an 8192 x 8192 pixel detector The Mosaic 1 CCDs are read out through a single amplifier per chip simultaneously to 8 controller inputs on 4 Arcon controllers For Mosaic 2 at CTIO 16 amplifiers 2 per CCD are working and can be readout simultaneously Unfortunately two of the CCDs in Mosaic 1 only have one working amplifier limiting Mosaic 1 to work in 8 channel mode The resulting mosaic array is a square about 5 inches on an edge The gaps between CCDs are abo
66. observing strategies Also we assume that the observer is already familiar with CCD cameras observations and reducing data The current versionis Mosaic 1 centric i e focused on the Mosaic camera available at KPNO Two very brief summary pages are at the front of this manual If you ve read this far and dont plan to read any further be sure you understand those 2 pages Development of the Mosaic systems is a continuing process although only very minor adjustments are being made at this time Throughout the lifetime of the instruments filters will be added old ones replaced and software enhanced This manual represents the status as of the date on the cover page We expect to revise the manual occasionally to include information gained during engineering runs as well as to reflect new filters This manual also appears as an HTML document on the NOAO WWW pages http www noao edu kpno manuals It can be downloaded as a PDF file via anonymous FTP to ftp noao edu cd kpno manuals binary get mosaic_man pdf We welcome suggestions for improving this manual 2 3 Supplemental Information Other manuals and Web pages to look at Other useful information regarding the use of the Mosaics CCDs and observing and reduction software can be found at NOAO Mosaic Camera web pages http www noao edu noao mosaic Direct Imaging Manual _ http www noao edu kpno manuals dim dim html NOAO KPNO Mosaic Web Page http www noa
67. ons are preset at the beginning of an exposure to be correct for the middle of the exposure but otherwise The 3 ADC modes in more detail are 1 Null Mode The ADC prisms are set to a fixed position that makes no correction for the atmosphere 2 Track Mode The positions of the ADC prisms are automatically updated at a periodic rate typically 60 second intervals to account for the changing zenith and azimuth directions of the telescope as it moves e g as it tracks during an observation or slews to a new position 3 Preset Mode The positions of the ADC prisms are set to a pre determined location as demanded by the mid point of the exposure In this mode movement of the ADC prisms is synchronized with the data acquisition sequence In this mode the ADC prisms do not move during the exposure 23 not moved We recommend using Track mode to improve the image quality with a minimum of attention to the ADC operations ADC Filter Mode In Modes 2 and 3 Track and Preset the positions of the prisms are dependent on the observing bandpass because the optimum corrections have a color dependent functionality Thus in using the ADC it is important to select the proper filter mode in the ADC GUI on rush While the ADC is not necessary to compensate for atmospheric dispersion when using narrow band filters the guide cameras have separate broad band filters see sec 2 7 that will see the effects of atmospheric dispersion Differe
68. ording Mosaic Data Recording your data to tape consists of allocating the tape drive and using MSCWEITS to write the Mosaic format files to a FITS format tape Every exposure produces 135 Mbytes of raw data and so after a good night an observer may have 100 images or 13 5 Gbytes of data Writing this volume of bits consumes a great deal of time and tape comparable to more than 5 hours and 3 Exabyte 8505 tapes possibly only 2 tapes if compression is used We offer a DLT 7000 tape drive at both the 4 m and 0 9 m and a drive is available downtown for those needing to transfer tapes to other technologies The DLT 7000 can write tapes about 3 times faster than the Exabyte 8505 and the tape cartridge holds 7 times the data volume While tape cartridges cost 70 they can hold roughly 3 nights of data In addition we also offer DDS 4 DAT drives at the 4 m and 0 9 m which can hold up to 30 Gbytes compressed on a 25 tape and can write an image in 40 seconds As an alternative we also offer two Exabyte 8505 compatible actually Eliant 820 drives at both telescopes For ease of portability we also offer DVD writers on tan nutmeg and emerald While all media can be purchased on Kitt Peak it is cheaper to bring your own Prices are as follows Exabytes 5 DDS 4 Dat 25 DLT 70 CD 1 DVD 2 Tape Drives and Device Names at the KPNO 4meter and WIYN 0 9m Computer IRAF Name UNIX Name Description Nutmeg KP4m mtb dev nst1 EXABYTE
69. osaicl 1 8315 1 8220 bin 1 1 gain 1 Observation finished Hit any key when ready guider working etc gt Image obj027 Mosaicl 1 8315 1 8220 bin 1 1 gain l1 Observation finished All exposures finished After each telescope movement the program pauses to allow time to reposition the guider hit any key when ready to continue At the end of the sequence the telescope will by default be returned to the starting position so that the process can be repeated in another filter The telescope positions are expressed as offsets in RA and Dec relative to the position of the telescope when the command is started they may be given in units of pixels or of arcseconds The file ditherdb todd dat contains a recommended dither pattern for filling in the interchip gaps Todd Boroson s canned dither scheme for the NOAO mosaic Offset relative to current telescope position RA pixels Dec pixels 0 0 200 200 200 200 100 100 100 100 The user may instead use their own file by setting the parameter offsets to the name of the file Phil Massey contributes the following table of aerial coverage when using the above dither offsets Entries in the table represent what fraction of the imaging area receives 20 40 60 80 and 100 of the integration time Fraction of Total Image area Central Image Area Exposure Time 8697 x 8642 8297 x 8242 20 4 6 0 0 40 4 4 0 0 60 4 4 4 9 80 11 8 13
70. ottom This effect can be measured and calibrated out but it can also be avoided with longer exposures since the shutter error is a constant offset in time 62 9 Appendix D Flat Field Exposures Typical Dome flat field exposures for each filter are given below These exposures should produce pictures having 5 000 10 000 ADU per pixel to stay within the linear regime note that each ADU represents 3 electrons so there is plenty of signal with these recommendations To minimize thinking at the telescope we tried to use the maximum voltage settings when possible 4m 53V 0 9m 100 Flat Field Lamp Settings and Exposure Times Filter 4meter 0 9m Lamp Exposure Lamp Exposure Setting Time Setting Time U High 53V 8s High 100 10s B Low 53V 18s Low 100 18s V Low 53V 12s Low 100 8s R Low 53V 12s Low 100 5s I Low 53V 15s Low 100 6s Halpha High 20V 9s Low 100 6s Halpha 4 High 20V 8s Low 100 60s Halpha 8 Low 100 60s i High 20V 9s Low 100 60s Ol High 53V 2s High 100 3s OIII 29 Low 100 28s g Low 53V 10s Low 100 4s r Low 53V 12s Low 100 5s r Low 53V 18s Low 100 6s Z Low 53V 228 Low 100 lls Wash M Low 100 3s DD051 High 20V 35s Low 100 18s VR Low 53V 8s Bw Low 53V 15s wh Low 53V 3s Low 50 5s 63 10 Appendix E Frequently Encountered Problems FEP Listed below are some problems that have been seen with Mosaic In some cases we have known solutions in other cases the solutions are more magical 10 1 Myste
71. pointer to an empty section of the desktop in the rush VNC window and hold down the right hand button to bring up the desktop menu Select the item End ARCON Session and release the mouse button After a few seconds the Arcon console acquisition status and countdown windows will disappear Any other windows on the desk top will be untouched so any processes running in them will be unaffected and you can continue to work in these windows Then close the VNC window by clicking the X in the upper right hand corner of the window e On tan emerald select Logout 4meter from the K start menu at the bottom left corner of the screen 4 6 OBSINIT At the very beginning of your observing run you should clean off all of the previous observer s images and files and reinitialize all of the IRAF parameters to their default values This must be done separately on both rush rust and tan emerald You or the instrument assistant can accomplish this as follows On tan or emerald e Log on using the observer login and password posted on the machine e Inthe IRAF Data Reduction window and any other IRAF sessions that may be running type logout The window should vanish e Select Unix Xgterm from the root menu Move the mouse to any blank area of the screen and hold down the right mouse button Slide the mouse down to Unix Xgterm e Inthe new window type obsinit and answer the questions appropriately 33 On
72. r can respond 1 Restart the Arcons Use the pull down menu on the data taking computer rush rust to select End ARCON session After the windows have successfully closed and the CPU has returned to zero select Start ARCON session from the 28 background pull down menu This will take a little while It may take several 3 5 Restarts to succeed Always try at least 3 Restarts before proceeding to the next level of severity listed below 2 Logout and Restart the Arcons End the ARCON session on the data acquisition rush rust computer and completely log out of the data reduction tan emerald computer Log back in and select Start Interfaces for MOSAIC CCD This will start the ARCON session DCA and Ximtool alt If there are still problems starting the ARCONSs go to level 3 3 Try some diagnostics open a Unix window on the Data Acquisition computer and then run the following diagnostic commands that check for communication with the Arcons xp source sun bin nexus0123 xp source sun bin aset0123 These should complete normally for all 4 Arcons If they fail to complete try a few more times If the errors are persistent power cycle the TRAM box see figures 4 4 1 At the KP4m power cycling the TRAM box is done remotely see below At the W0 9m this is done manually see below REMOTE POWER CYCLING OF THE TRAM BOX 4M ONLY a Open an xterm window on Rush b Telnet 4m nexus power 140 252 52 74 c Log in as 4meter en
73. read images using mscwfits DDS 4 DAT 49 54 sec Exabyte 1 29 1 14 DLT no compression 0 37 1 02 DVD writer 4 GBytes and CD RW are also available Please be off the computer by noon of your last day You can purchase DLT DAT and Exabyte tapes as well as DVDs DVD R 4x at the Kitt Peak Administration office but bringing your own is cheaper Calibration data If you wish take darks matching expected exposure times although we have not measured significant dark current with the current version of the instrument Take dome flats and or twilight flats night sky flats work even better Take zeroes i e biases Darken the dome for darks and zeroes 2 Introduction 2 1 Instrument Overview The NOAO CCD Mosaic cameras are wide field imagers having 8192 x 8192 pixels At the KPNO 4 m where the pixels are 0 26 on the sky this provides a field of view of 36 arcmin on a side At the WIYN 0 9 m where the pixels are 0 43 on the sky the field of view is 59 arcmin on a side Each unbinned exposure with the camera requires 2 34 of over head including exposure preparation time and CCD readout When used with binning the readout time for MOSAIC is reduced but the preparation overhead remains When used with 2x2 binning the total exposure over head is 1 06 The CCDs are read out through 4 Arcon controllers to a data taking computer known as rush at the 4 m and rust at the 0 9 m which serves as an intermediary data gateway The p
74. rious messages appear and pictures cannot be taken Occasionally the Arcon controllers get into a weird state See section 4 4 for recovery procedures 10 2 Data Doesn t Show Up on Reduction Computer Occasionally and we don t yet understand why or when the Mosaic reads out but the data fails to transfer to the reduction computer If you act now you may be able to save the picture Restart the DCA on tan emerald Type recover on the acquisition computer rush rust in the IRAF data taking window We have only seen this problem very occasionally when the Arcons are restarted multiple times Unfortunately recover generally will not salvage a readout that hangs after only a portion of the image has been readout 10 3 Echo Images in adjacent CCD Cross Talk Due to electrical cross talk between the CCD pairs controlled by a single Arcon controller each Arcon runs 2 of the 8 CCDs the data stored for one of the CCDs in each pair has an echo of the other Specifically the stored pixel values for the affected CCD are the true values plus a very small fraction of the counts measured in the paired CCD The effect is most noticeable for saturated and nearly saturated stars gt 20 000 ADUs whose echoes appear at the 10 to 30 ADU level in the second CCD For Mosaic 1 we see echoes in CCDs 1 3 6 8 arising from the CCDs 2 4 5 and 7 respectively CCDs 2 4 5 and 7 show no sign of a matching echo from their paired CCDs The Mosa
75. rush or rust If an Arcon session is active on rush or rust e Shutdown the Arcon session Move the mouse to any blank section of the desktop and hold down the right hand button Select the item End ARCON Session and release the mouse button e Log out of any IRAF cl sessions that may be running e Select Unix Xgterm from the root menu Move the mouse to any blank area of the screen and hold down the right mouse button Slide the mouse down to Unix Xgterm e Inthe new window type obsinit and answer the questions On rush or rust If an Arcon session is not active on rush rust e Open a xgterm window in the VNC window for rush rust e At the rush UNIX prompt type obsinit and answer the questions The reason for the above procedure is that you cannot have IRAF running during an obsinit because parameters will not be reset correctly Make sure that you have logged out of each IRAF window before running obsinit Note that the user has the option of selecting whether CNTL z or CNTL d will be the default for an end of file command the former is the standard at NOAO but the latter is the standard at many other places If you simply wish to set all of the IRAF parameters back to their default values you may run this in the middle of your observing run without losing any files 4 7 Re starting the MSE and related software The software MSE which controls the instrument filter track TV cameras etc and the communications so
76. sed on the observe command One consequence of this is the user s terminal will be tied up while the script is running If you realize you have made a mistake after starting the script and want to stop execution of doobs first type Ctrl C which will abort the script then type abort stop which will terminate the sequence of exposures currently being executed 4 10 5 Grids and Dithering If you want to make a cosmetically clean image it is necessary to take multiple exposures at slightly different telescope pointings to fill in the gaps between CCDs and eliminate bad columns Two scripts have been provided to help in this task e mosdither takes images at a series of positions read from a file cl gt lpar mosdither exposure 420 Exposure time title Tr7 I dithered Title for pictures offsets ditherdbStodd dat file containing offsets npics 1 Number of exposures at each position units pixels units of offset gohome yes return to starting position at end of grid guider_contr offon Guider control mode resume no start at position_number rather than beginning position_num 2 starting line number in file old_mode no run in old but tested mode fd internal use only mode ql 39 cl gt mosdither Exposure time 0 420 Title for pictures test Tr7 I dithered Filter in wheel one I Telescope focus 3000 6000 4400 4440 Filterl I Telfocus 4440 00000 Image obj026 M
77. t Linux box with a 3 4 GHz Pentium 4 CPU and 2 Gbytes of memory 2 On the central console tan 0 0 or emerald 0 0 right click on the background to bring up the menu of options The top option is Start Interfaces for MOSAIC CCD Select this option This will open the VNC client in tan 0 1 or emerald 0 1 in which the windows from rush or rust will be displayed It will also start the DCA Data Capture Agent and associated GUI of the data handling system in the center monitor tan 0 0 as well as the Ximtool display in tan 0 2 or emerald 0 2 displayed on the right monitor The right monitor is only an 8 bit display to accommodate the current version of X imtool a new version with 24 bit color is under development and should only be used for the display window or there will be problems with the allocation of colors to the display window We are still working out some undesirable features in this display If you would rather use DS9 as an option for the image display kill the Ximtool window right click on the background of tan 0 2 to bring up the menu and select DS9 DS9 should work fine as your display device If you want to switch back to Ximtool you will have to log out of tan and then log back in and restart as described above This VNC stands for Virtual Network Computing a software program that allows one to view and manipulate windows on another computer We use VNC to remotely view the Arcon control computers rush at the
78. ter the password d This window will print some information Type off 1 and confirm with Yes e Count slowly to 50 Type on 1 and confirm with Yes MANUALLY POWER CYCLING OF THE TRAM BOX 0 9M ONLY a Locate the TRAM box in the computer room see figure 4 4 1 below b Turn the power on the TRAM box off wait 30 seconds and turn the power back on Try the xp commands again If the xp commands succeed then try the following commands from a Unix window on the Data Acquisition computer This is a subset of the normal Arcon startup 29 cd arcon_user This will take a few minutes and tries to bring up the Arcons completely but not the other windows GUI IRAF If it fails the first time try a few more times If it succeeds or fails type arsh stop to exit the window If successful attempt another Arcon restart If it fails try 3 more times If you still cannot get arcon_user to complete go to level 4 4 Reboot the data taking computer rush rust a End the ARCON session by selecting End ARCON session on the Data Acquisition computer rush rust b Open an xterm window from the background menu on rush rust c Type reboot rush at KP4m or reboot rust at W0 9m d Wait a couple minutes for the reboot to complete While waiting cycle the power on the TRAM box see the TRAM box power cycling procedures above e Restart the VNC client to rush rust via the background menu on tan emerald and start t
79. the field center with the pixels in the field corners being 6 smaller in the radial direction 54 and 8 smaller in area given the complete astrometric description of the field Pixels in field corners thus would properly report only 92 of the sky level seen in the field center even with uniform sensitivity At the same time the same number of total photons would be detected from a star regardless of how many pixels the PSF would be distributed over Forcing the sky to be uniform over the image would have the deleterious effect of causing the photometric zeropoint to vary from center to field corners by 8 Note that this effect is different from vignetting where the flux actually delivered to the image margins is less than that at the center an effect that is corrected by the flat field In practice the photometric effect of the variable pixel scale can be ignored provided that the reduced images will be part of a dither sequence to be stacked later on As discussed below prior to stacking the images they first must be re gridded to a tangent plane projection which has pixels of essentially constant angular scale This is done with the MSCIMAGE task which re grids the pixels and has a flux conservation option that can scale the pixels photometrically by the associated area change If this function is disabled then improperly flattened images will have a uniform zero point restored with this option turned off In short the flat field
80. uadratically by 6 5 out to corners PSF quite constant across the FOV but 6 larger in linear scale at the corners Faint 2600 pixel wide image of the pupil in each image 1 at UI 0 8 at BVR 2 4 in narrow band filters 9900 at 17C 10200 for U approximately 300 unit offset for U band change with temperature 90 units per degree C Atmospheric Dispersion Correction For broad band filters use ADC in track mode with appropriate filter selected For flat fields and narrow band exposures use the null position or closest broad band filter mode in wavelength WIYN 0 9 Meter formerly KPNO 0 9m Parameters Count Rates FOV Scale Image quality Typical focus At UBVRI 20th mag U 2 B 14 V 15 R 16 I 9 e sec 59 x59 XIMTOOL Orientation North left East up 0 43 pixel PSF fairly constant across the field but a 20 30 focus unit tilt is present 31000 at 10C 31050 for U change with temperature 80 units per degree C Data Acquisition Acquisition commands are given on computers named rush at KP4m or rust at W0 9m These computers are currently accessed by the user via a VNC display on tan at KP4m and emerald at W0 9m Data Reduction At the KP4m images can be inspected and processed using the computers tan or nutmeg At the W0 9m this work is done on emerald All the Commands That Are Likely To Be Needed Observing Commands on Rush at KP4m or Rust W0 9m observe take one or mor
81. ures Gary Bernstein motivated this section Differential Reitaction Ancsec H i TEETE PEPEE FEHEDES EEE 4m H H i E H i F i i E i FASES i i QmenEd Teme po PO oc Cogs be PRE PRP REEL ERE O RB PRR ORE HT H H H H H H i E k i io 12 14 16 13 20 22 24 25 25 30 imass Figure B 1 This plot shows the differential prismatic distortion due to atmospheric refraction over the extent of the Mosaic field The difference in angular displacement of a star between the center and corner of the Mosaic array is shown as a function of airmass for the 4m and 0 9m cameras Note that this effect does not vanish at the zenith as even the angular extent of the Mosaic field at the zenith is large enough for differential prismatic distortion to be present The particular curves shown are for an STP atmosphere The actual displacement will vary with temperature and in general will be slightly lower given the altitude of KPNO The prismatic distortion will also occur only parallel to a vector pointing to the horizon the center to corner displacement is thus meant only to be representative of typical angular distances within the Mosaic field Note that as a Mosaic field transits a range of airmasses as might occur in a dither sequence the differential prismatic distortion will vary over the sequence 61 8 Appendix C Issues About Photometry A common goal of observing with Mosaic is to derive photometric
82. ut 0 7 mm in the row direction and 0 5 mm in the column direction See Figure 3 1 1 showing an image labeled with chip numbers The Mosaic Imager is populated with thinned AR coated SITe CCDs These chips have only minor flaws that have little effect on their scientific performance but they do require careful calibration to attain excellent flat fielded images Figure 3 1 1 A Flat field R band map of the CCDs in the Mosaic with their extensions im1 im2 im3 as used in the IRAF nomenclature see section 5 10 QE Relative to Average Figure 3 1 2 shows the average QE for the 8 CCDs Individual CCDs deviate from this curve as shown in Figure 3 1 3 Average QE Wavelength nm Figure 3 1 2 The average QE for the 8 SITe CCDs in Mosaic I OOF 009 008 D ex oS Q o o o Wavelength nm 0001 0001 Figure 3 1 3 The QE differences relative to the average for the 8 SITe CCDs in Mosaic I Also shown are the readnoise RN and gain GN values for each CCD 11 3 2 The Dewar The Mosaic dewar is a large 6 3 liter vacuum vessel radiatively coupled to the CCD mount It is the large round cylindrical object in the center of Figure 3 2 1 The hold time of the dewar is 17 hours It is filled by an observing technician at the start and end of each night Several temperatures within the dewar are monitored and displayed in the Mosaic Graphical User Interface GUI The CCDs should be between
83. w that asks you to pick the appropriate mode If you would rather have the system automatically decide which is the correct mode you can unclick the selection button in the GUI see figure 3 9 1 The default mode for each 24 filter is listed at http www noao edu kpno mosaic filters filter_names Note that the default of start up mode of operation is for the system to prompt the observer to confirm the ADC mode before starting the first observation with a new filter 25 4 Software 4 1 Logging in and firing up the Arcon Mosaic software Before you can begin to take data you must log in on both the data acquisition rush rust and data reduction tan emerald computers We are currently controlling the Mosaic 1 with rush KP4m or rust W0 9m with the data handling and analysis being done with tan KP4m or emerald W0 9m Both emerald and tan have 3 monitors labeled tan emerald 0 0 center monitor tan emerald 0 1 left monitor and tan emerald 0 2 right monitor At the 4m there is an additional data reduction computer nutmeg which has a dual processor Note that the home directory for tan is mdl 4meter and on nutmeg is md4 4meter To begin your observing session you should follow these steps at either the 4m or 0 9m 1 Log on to tan emerald as user 4meter 36inch The computer tan is a fast computer with two CPUs 1 667 GHz AMD processors and 1 Gbyte of memory operating under Linux The computer emerald is also a fas
84. y background or zeropoint In practice we have found that the stacking works beautifully with data obtained under clear conditions and with no bright stars near the fields on the other hand we have found that simple reduction strategies produce very poorly stacked images if the shape of the sky over the field or scattered light contributions varied over the course of a dither sequence or over the course of the night used to define the sky flat 55 The first step in stacking the reduced Mosaic images is to register them to a common coordinate system This is done with the MSCZERO and MSCCMATCH programs The MSCZERO routine can be used to set the coordinate system origin for any given image given a known position or even ad hoc position for any star MSCCMATCH produces a revised astrometric solution for each dithered image this is essential because of small linear shifts during the dither process and because of rotations introduced by differential atmospheric refraction across the field There are three important uses of MSCZERO The first is to set the coordinate zero point fairly accurately and then read back coordinates With a reference star one can obtain useful real time coordinates at the telescope The second use of MSCZERO is to identify a list of stars in one fiducial image that will be located in the other images in the dither set A third use is to reset the origins of the other images in the dither set to match the fiducial image

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