DAO Telescope User Manual
Contents
1. Full well Ke p Gain e ADU 1 5 Range bits 16 Range ADU 64K QE 400nm 2 QE 500nm 20 70 QE 600nm 35 72 QE 700nm 47 70 QE 800nm 32 57 QE 900nm 23 33 QE 1000nm 6 10 Abreviations in the above table are as follows e electrons Ke kiloelectrons ADU analogue to digital units QE quantum efficiency The SITe 3 chip SITe is a descendent company from Tektronix is identical in physical dimensions and similar in other properties to the Tek 2 chip apin a oe eA P ECA L ETN a EEIN Ea Eos oO Note that thinned backside illuminated CCDs when illuminated with monchromatic light display interference fringing ina manner that is only partially removable by flat fielding The effect is most pronounced at red and near IR wavelengths eg the band and limits the signal to noise achievable when such chips are used for spectroscopy The DAO CCD s are fitted with identical dewars and hence any CCD may be used on the 1 85 m Newtonian focus the 1 85 m spectrograph or either of the 1 22 m coud spectrograph configurations All the current CCDs operate with compatible hardware and DICE DAO Instrument Control Environment software thus their operation appears identical to the user By the raster command the observer has control over the area of the CCD to be sampled and can invoke on chip binning For spectrographic use it is common to sample2. epoch to the current epoch negating the need to precess coordinates separately See the command EPOCH Get list An observing list can be uploaded into the TCS allowing objects to be referenced by a number This is quicker and less prone to errors in the wee hours of the morning USEFUL COMMANDS EPOCH yyvy vy Sets the epoch that coordinates entered with the move command will be precessed from Year may be entered on command line or will be prompted for Decimals are optional If no year is given on the command line and the prompt is answered with only a carriage return the epoch will be set to current This is the year on the screen above the OBJECT R A see move GOTO hh mm ss ss dd mm ss s Goto an Hour Angle and Declination The telescope will not track If the motors were off and the brakes on they will switch on and off If coordinates are not given on the command line they will be prompted for Coordinates may be truncated and colons must be used MOVE hh mm ss ss dd mm ss s Move to a Right Ascension and Declination and begin tracking If the motors were off and the brakes on they will switch on and off If coordinates are not given on the command line they will be prompted for Coordinates may be truncated and colons must be used PARK Turns on the motors and releases the brakes if not already so then moves the telescope to the normal park position zenith No parameters required SETDATE
3. yy mm dd Sets the system date Shouldn t normally be needed If date isn t entered on the command line it will be prompted for SETST hh mm ss Sets the sidereal clock Shouldn t normally be needed If time isn t entered on the command line it will be prompted for Colons are required SETUT hh mm ss Sets the UT clock Shouldn t normally be needed If time isn t entered on the command line it will be prompted for Colons are required STOP Turns off the motors and engages the brakes on both axis regardless of the state of the system tracking still or slewing Used at the end of the observing to turn things off and to reset the system if it is mis behaving File home sarty public_html Astronomy dice txt How to start DICE gt dice Current detector SITe 2 Current mode of observation spectroscopy Useful DICE commands autowrite_on autowrite_off turns on or off the autowrite function Should be on for most normal observing Note that frames will be written when cycling if autowrite is enabled bye exits the controller environment Should clear up the windows Should be entered in the controller window cycle exp_time prompts for exp time if not entered on command line and number of items to take Will write them if autowrite is enabled observer name to enter the observer into the system This will appear in the FITS header quit stops a current exposure prematurely raster row
4. Sun Workstations from the observer s rooms The DAO Instrument Control Environment DICE software presents a graphic user interface that prompts the user for the required operating commands Most functions are performed by the click of a screen button by the mouse The DICE program allows the user to define the area of the chip to be sampled and initiates an SAOimage window where the data frame is fully displayed Monitoring that the CCD remains at operating temperature during the night can be performed by displaying row or column plots of bias frames or of data frames including the overscanned strip The observer s rooms also have Xterminals with which data can be transferred to an appropriate disk for further storage and processing The workstations and Xterminals are linked to the the rest of the computer system via Ethernet fibre optic link 14 07 07 10 13 PM NRC HIA Dominion Astrophysical Observatory http www hia iha nrc cnre gc ca dao detect_e html Published 2003 02 27 A Important Notices 5 of 5 14 07 07 10 13 PM NRC HIA Dominion Astrophysical Observatory http www hia iha nrc cnre gc ca dao filters_e html ivi Herzberg Institute of Astrophysics DAO Homey About DAO gt Public Outreach gt Facilities v Telescopes Detectors Spectral Data Filters Information for Visiting Scientists Facilities Evaluation Form Observing at DAO gt Contact DAO gt lof 2 National Research Conseil national Can
5. _ I 1 SS GC NIN w O N 40 9 i oO w D on BL ee 2121H 2122 281 aE 15 0 3 0 2121 3 0 2 0 Bo 1 0 1 0 ee N O _ NO w N O O N kE ao N eo _ iso 2 z 2 a T o S 2 m Telescope Spectrograph Configurations where the last two columns give approximate exposure times in minutes for a sixth magnitude star exposed to approx S N 30 14 07 07 10 34 PM NRC HIA Dominion Astrophysical Observatory http www hia iha nre cnre gc ca dao 12_e html 5of 8 lla photographic emulsions respectively Because of the wide dynamic range of CCDs actual exposure times may vary considerably depending on the signal to noise required by the observer A single scale exposure meter allows comparison of exposures taken under different conditions of seeing and transparency For the spectrograph configurations using 830 groove mm gratings such as 9682M 9681M 3282 and 3281 which all use gratings replicated from the same master grating efficiency curves are available here for first order reflection and second order reflection to allow an informed choice of which order will perform best at a given wavelength On these plots the reflectance of a freshly aluminized surface is also shown for comparison Image Slicers There are four Richardson superpositioning image slicers as follows 1 2 m T
6. focus using either the HST Guide Star Catalogue GSC or the Digital Sky Survey DSS Both these resources are online at DAO and may be summoned at the telescope as needed if you do not have time to check them before your run The Digital Sky Survey may be accessed directly or from the CADC pages and shows stars to much fainter limits than the TV guider will see without direct photometric information The stars of the GSC on the other hand are all sufficiently bright to be suitable 14 07 07 10 11 PM NRC HIA Dominion Astrophysical Observatory http www hia iha nre cnre gc ca dao 185_e html for guiding with the Newtonian guider Published 2003 06 12 A Important Notices 9 of 9 14 07 07 10 11 PM NRC HIA Dominion Astrophysical Observatory http www hia iha nrc cnrc gc ca dao detect_e html i f National Research Conseil national Can da Council Canada de recherches Canada a a ContactUs Help Search Canada Site Home Centre of Sunrise NRC Site the Universe Staff List Sunset SiteMap BRC CARC y when CCD Digital Detectors NEWS DAO Homey Technical questions You can email us at HIATelescopesupport nrc cnrc gc ca About DAO gt ee Charge Coupled Devices CCDs Facilities v Telescopes Because of their high quantum efficiency low readout noise large dynamic range wideband spectral sensitivity and excellent dimensional stability charge coupled devices are now the Spectral Data detectors of choice for mo
7. from f 145 back to f 30 Actually there are two interchangeable lenses one coated for maximum transmittance in the blue lt 5000 A the other for the red gt 5000 A spectral region The lens selected should conform with the mirror set in use and of course with the spectral region being observed At the coud focus an image slicer ensures high throughput to the coud spectrograph where one of two optical paths may be selected A 32 inch focal length spectrograph camera can be combined with one of six available diffraction gratings of 300 600 830 and 1200 grooves per mm which have various blaze angles and some of which are efficient in either first or second orders These yield many possible reciprocal dispersions of which 6 5 10 18 and 41 A per mm are the most commonly used Alternatively the beam can illuminate a mosaiced 830 groove per mm grating and a 96 inch focal length camera to give a spectrum in the red 1st order at 4 8 A per mm or in the blue 2nd order at 2 4 A per mm The corresponding resolution of all these spectrograph configurations ranges from 0 07 to 1 2 A A CCD may be mounted at the spectrograph focal surface for highly efficient low noise spectral measurements The disadvantage of these detectors is their small physical dimension which allows coverage of a rather modest wavelength range A popular instrument specific to the 1 2 m telescope is the designed for photoelectric measurement of Doppler shift
8. the 112 micron width of the IS32 s passes as much light as would a 450 micron slit neglecting internal reflective losses within the slicer A second advantage is that they enable light slices passing from the grating to the camera to pass above and below the flat mirror used to reflect light returning from the camera into the detector thereby avoiding internal obscuration from the on axis design An ordinary slit is very inefficient for stellar sources at this focus and is rarely used It may be used for spectroscopy of extended sources such as cometary comae where the image slicer presents no advantage in order to retain one dimensional spatial resolution along the slit The ordinary slit is adjustable for widths of 75 microns 0 003 inch and larger When using the ordinary slit the square mask on the collimator should be replaced with a round one Radial Velocity Scanner spectrograph a removeable diagonal mirror just before the focal surface directs the light into the scanner The instrument is based on the prototype RVS built by Roger Griffin at Cambridge Observatories That is a mask resembling an ultrahigh contrast negative of a late type stellar spectrum is scanned back and forth through the focal surface when the windows of the mask coincide in position with the principal stellar absorption lines a minimum amount of light is passed through to a photomultiplier the position at which this minimum occurs is a measure of the Dop
9. the TCS has deemed to be a safe intermediate position final slew will begin immediately after the intermediate position is achieved In particular on the safe zone map the telescope will move from zone 7 to zone 2 through zone 1 from zones 2 to 6 through zone 3 and so forth As presently cabled the telescope is used with the tube east of the piers and must not be reversed so it is not possible to circumvent the limits imposed in the northeast and southeast directions It is possible to move either dome or telescope under manual control with the handset in which case the TCS will not impose the plotted limits instead the operator must use extreme caution to ensure they are respected and that the spectrograph does not approach either pier Tracking cannot be engaged under manual control so the TCS must be returned to auto control for observing Spectrograph Configurations amp Exposure Times The Cassegrain spectrograph is an all reflective system except for the refractive field flattener just before the detector Its optical elements are a 1750 mm focal length off axis to avoid internal obscuration collimator a diffraction grating and a 538 7 mm 21 in focal length f 5 camera a diagonal mirror and the field flattener The collimator and camera mirrors exist as two interchangeable optics sets differing in their reflective 14 07 07 10 11 PM NRC HIA Dominion Astrophysical Observatory http www hia iha nre cnre gc ca dao 18
10. 1 sec exposure allows detection to 17th magnitude a 10 second exposure to 18 5 magnitude view slit 1 second exposure allows detection to 15th 14 07 07 10 11 PM NRC HIA Dominion Astrophysical Observatory http www hia iha nre cnrc gc ca dao 185_e html 3 of 9 magnitude Manual guiding of the telescope either directly on the slit image slicer or offset on a guide star as seen on the TV guider screen is accomplished with the keypad buttons on the TCS keyboard These buttons move the telescope stepwise by preset amounts usually 0 5 when guiding in the north south or east west directions for each keystroke Alternatively an autoguider may be invoked at the TCS terminal for automatic guiding on longer exposures The TCS will not allow you to set the telescope outside safe limits the permitted range of hour angle and declination is plotted on the safe zone map There are a number of potential danger areas within the physical range of motion of the telescope collisions between the spectrograph and either pier the telescope tube and the north pier the detector and the hour angle drive housing and collision between the telescope tube and the remaining portion of the Newtonian elevator access platform on the dome If the TCS accepts any given target without returning a limit error to the user it will automatically negotiate the danger areas to set on that target This often results in an apparent slew to a wrong position which
11. 4 1 3Ang 2 0Ang 4 0 Ang RESOLUTION AT FOCUS 60Ang mm 120Ang mm 2 2 Ang 4 4 Ang 3 0 Ang 6 0 Ang 4 2 Ang 8 4 Ang 5 4Ang 10 8 Ang 8 0 Ang 16 0 Ang For long slit spectroscopy the scale is 6 2 per mm at the slit 20 1 per mm at the spectrograph focal plane The slit length is adjustable with a decker to 20 40 or 60 corresponding to widths of 1 2 or 3 mm on the detector There is however a perceptible deterioration of resolution at the tips of the lines with the longest 60 slit For well guided stellar spectra the sky spectrum will naturally be exposed alongside the stellar spectrum and recorded on the CCD detector Because of the proximity of the city of Victoria mercury and sodium emission features from the sky will usually be recorded on the spectra of stars around 12th magnitude and fainter depending on the quality of the night the direction of the star and the wavelength region under observation At about the same magnitude the solar spectrum can be a contaminant at full moon under hazy skies In these situations 5 of 9 14 07 07 10 11 PM NRC HIA Dominion Astrophysical Observatory http www hia iha nre cnrc gc ca dao 185_e html 6 of 9 it is quite important to detect and subtract out the sky contribution to your spectra Richardson type superpositioning image slicers may be used to optimize slit efficiency at the higher resolutions where sky subtraction is not required Four image slicers are av
12. 5_e html 4 of 9 coatings The default set designated Al has standard aluminum coatings and is useable over the entire range of the spectrograph or approximately 3000 9500 A The other optics set is gold Au coated for better reflectivity in the red near infrared region and is available if requested The various configuations of the spectrograph are listed below The designation 21181 refers to the combination 21 in focal length camera 78 hundred grooves per mm grating 1 st order and so on All these gratings are used in first order The wavelength of peak blaze efficiency is so designated B G R indicate peak efficencies in the blue green or red IR regions Peak blaze efficiencies are typically around 80 The last column gives approximate exposure times in minutes for approx m 12 magnitude star exposed to approx S N 30 at the wavelength of the blaze with the SITe 5 CCD as detector See the section on digital detectors for a comparison of detectors in their readout noise and spectral response characteristics In practice exposure times also vary widely according to detector binning grating rotation spectral type of the star spectrograph aperture and with the quality of the night seeing and transparency The best guide for exposure times is usually to check in the observing log book for an application similar to your own particularly spectrograph configuration wavelength and detector and noting the exposure times an
13. Description The Telescope Control System TCS in it s simplest form just accepts a target and attempts to keep the telescope at that target Only a few commands are needed to use the TCS in its simplest form There are also a number of facilities to ease its use The following sequence is recommended to reduce the chance of problems Start up 1 MIU Mechanical Interface Unit located behind the observer s room in electrical rack on floor turn the key to the AUTO position press the emergency stop RESET button 2 COMPUTER the terminal is on desk to right of door you can find the system in one of 4 states Hit the lt cr gt C RETURN key on the terminal and check the prompt 1 72inch gt prompt This is the program prompt Hopefully this is running and you can go on 2 hyphen prompt This is the operating system Type start followed by a lt cr gt to start the program 3 period prompt This is the BIOS Either something has gone wrong or it has been accidently left in this state Type b followed by a lt cr gt When the prompt appears GOTO 2 4 No response Try turning off and on the terminal If still no response locate the TELESCOPE CONTROL INTEL in the rack and press the red button on the lower left of the computer and go back to the terminal An asterisk should appear followed by some diagnostics followed by the prompt within a couple of minutes GOTO 2 A Few Thing
14. _size col_size row_start col_start par_bin ser_bin For changing the raster If not all 6 parameters are on the command line all will be prompted for Note slightly different convention for rastering from Intel version save_default_raster will save the default raster in an init_dice_session file so that raster is recommended each time DICE is started up start exp_time starts an exposure of the detector Will prompt for an exposure time if not entered on the command line The object name will be prompted for weycle exp_time as cycle but writes the frames even with autowrite not enabled write causes the system to write the archive exposure The result of this appears in the status window Files can t be re written Page 1 NRC HIA Dominion Astrophysical Observatory lof9 i Herzberg Institute of Astrophysics DAO Homey About DAO gt Public Outreach gt Facilities v Telescopes 1 85 m Telescope gt 1 2 m Telescope Detectors Spectral Data Filters Information for Visiting Scientists Facilities Evaluation Form Observing at DAO gt Contact DAO gt http www hia iha nre cnre gc ca dao 185_e html National Research Conseil national Can da Council Canada de recherches Canada a a Frangaie__ comtact Help Search Canada Site Home Centre of Sunrise NRC Site Library _ the Universe ESMEE Library EZITE Sunset The Plaskett 1 85m Telescope Spectrograph and Imager N
15. a conventional slit Fe Ar and Cd Ne hollow cathode sources provide wavelength calibrations and a tungsten lamp source provides flat field calibrations for the spectrograph configurations Telescope Control System The TCS will automatically position the telescope and dome to star coordinates of any designated epoch as entered on the keyboard Alternatively the TCS can set by star number from a list on the UNIX netwark See the section on Before You Come for the requirements for such a target or get list The TCS can also accept offsets from a reference star which can be useful for setting on very faint objects The positional encoders are accurate to approximately 1 but residual errors in the system limit the whole sky setting accuracy to something like 20 For Cassegrain spectroscopic observing the TCS terminal also controls the light feed into the spectrograph and or TV viewer guider By choice of diagonal mirror above the Cass focus the monitor for the TV guider will display either view solid a full 7 x 6 alpha x delta field to magnitude 17 to allow target identification and centering or view holey the outer ring of the 7 x 6 field to allow offset guiding while the slit is illuminated by the target object or view slit direct viewing of the slit or image slicer aperture to allow guiding on the target object itself The field of view is determined by the dekker length adjustment view solid or view holey
16. ailable for the 21 in camera they have either blue B or red R coated optics for maximum throughput and come in two levels of resolution The resolution of the very short image slicers VSIS21 is approximately that of the 0 8 arcsec slit given in the above table Resolution of the regular IS21 slicers is usually limited by the pixel size of the detector 1 8 m TELESCOPE IMAGE SLICERS APERTURE PROJECTED SLIT DESIGNATION SIZE WIDTH IS21B 3 x 5 20 microns IS21R 3 x 5 20 microns VSIS21B 4 x 4 40 microns VSIS21R 4 x 4 40 microns Newtonian Focus Imaging The modified Newtonian system on the telescope allows direct imaging at f 5 with any DAO CCD or IR detector A flat secondary mirror is installed below the Cassegrain secondary to direct the axis of the light cone at a 30 degree angle to the primary optical axis to form a focus about half way up the telescope tube The scale at this focus is 22 5 per mm which provides a well oversampled 9 2 x 9 2 field with the SITe 5 CCD The TV guider for the Newtonian focus is operated from the observer s room and displays a field 7 5 x 6 5 alpha x delta on the monitors As controlled by the point command of the TCS the field by the TV guider can be either the the co ordinate position entered on the TCS for field verification or else a guide field offset from the detector field for guiding during an exposure Since the pointing errors of the telescope are small compare
17. alues for the now defunct SITe 1 CCD detector are as follows courtesy of Dave Balam University of Victoria V coeff 0 023 b v 0 990 v r 0 956 all are 0 02 r i 0 895 Approximate transformation coefficent values for the Tek 2 CCD detector prior to the last realuminization of the mirror were V coeff 0 005 0 008 b v 0 944 0 015 v r 1 014 0 011 Dave Balam University of Victoria reports on extinction and transformation coefficients for SITe 5 from the night of July 9 1998 as follows k v 0 258 k bv 0 159 V coeff 0 038 all are 0 01 b v 0 940 solution from 13 Landolt standard stars and M92 standards The terms are defined by Hardie Photoelectric reductions Stars and Stellar Systems CCD standards field on these pages gt For IR imaging a cooled filter wheel accepting up to eleven 1 2 inch round filters is mounted within the Dewar itself Infrared filters available include J H and Cowie K filters with central 14 07 07 10 11 PM NRC HIA Dominion Astrophysical Observatory http www hia iha nre cnrc gc ca dao 185_e html 8 of 9 bandpasses of 1 25 1 65 and 2 1 microns respectively Filter selection is controlled from the workstation in the observer s room Transmittance curves for the above filters are available on request Before You Come In preparing your observing program the following points should be kept in mind In addition to your base program plan for a
18. at the imaging focus The current style of operation and complement of instruments is comparable to equipment found at all major observatories thus enabling students to gain experience directly relevant to the use of larger telescopes elsewhere From the observer s room on the north side of the observing floor the Telescope Control System TCS monitors the position of the telescope 14 07 07 10 11 PM NRC HIA Dominion Astrophysical Observatory http www hia iha nre cnrc gc ca dao 185_e html 2 of 9 while a Unix workstation controls data acquisition with instrument control software DICE that is uniform for all detectors and telescopes at DAO An adjacent Xterminal allows field verification from the HST guide Star Catalogue or the Digital Sky Survey and permits immediate data transfer and processing if desired Routine observing operations can be performed with ease by a single observer Observing manuals are available on line to guide the observer The Cassegrain spectrograph is particularly versatile its various apertures gratings and detectors allow spectroscopy of objects down to 16th magnitude at resolutions ranging from 0 4 to approximately 20 A lambda Delta lambda approximately 200 15000 with signal to noise ranging up to 150 or better The practical range for spectroscopy is 3600 A to 9500 A subject to the constraints of atmospheric transmission Long slit spectroscopy and sky subtraction features are provided by using
19. ation a wider filling tube is used reducing the filling time to a couple of minutes and reducing the hold time to about 4 hours HOWEVER the hold time at operating temperature depends on the individual CCD Dewar the degree of vacuum of the Dewar which itself depends on the elapsed time since being pumped down and its thermal history during that interval and the orientation of the Dewar cannister at the telescope or spectrograph i e whether it can be fully filled or not In normal circumstances the SITe 1 CCD at the 1 8 m imaging focus should remain at operating temperture for up to 12 hours For the UBC 1 CCD at the 1 2 m coude focus the cool down time is 3 hours and the hold time 7 hours It is always best to consult with telescope support staff as to the current hold time for your particular detector or look for messages in the observing room from them on this matter The Dewars may require pumping to regain a high vacuum if they do warm up Daytime refilling of the CCD Dewars is usually performed by the telescope support staff on weekdays On weekends the observer is responsible Automatic refilling of the Dewars via a timer controlled valve is an option available to weekend observers For infrared observing a NICMOS array detector is available contact the Telescope Group at HIATelescopesupport nrc cnrc gc ca for details Data Acquisition Computers The acquisition of data from the CCDs and the IR array is performed on
20. carfe 1982 PASP 94 1017 a McClure Fletcher Grundmann amp Richardson 1985 14 07 07 10 34 PM NRC HIA Dominion Astrophysical Observatory http www hia iha nre cnre gc ca dao 12_e html Stellar Radial Velocities AU Colloquium 88 p 49 Before You Come program stars into a data file before your run commences as it will greatly expedite your observing procedure The format for such an observing list is the same as for the 1 8 m telescope Published 2003 05 12 rY Important Notices 8 of 8 14 07 07 10 34 PM
21. ctrographs in the coud room each with its own collimator camera combination 96 For highest dispersion a 7600 mm focal length collimator illuminates a mosaic of four identical 830 8 g mm gratings whose dispersed light is focussed by a 2432 mm 96 in focal length on axis camera at f 8 32 For intermediate dispersions one of two 4500 mm focal length collimators illuminates one of six available 14 07 07 10 34 PM NRC HIA Dominion Astrophysical Observatory 4of8 http www hia iha nre cnre gc ca dao 12_e html gratings whose dispersed light is focussed by an 813 mm 32 in focal length on axis camera at f 5 The two collimators differ only in the aspheric correction for spherical aberration choice of collimator is dictated by choice of grating Spectrograph configurations are designated thus 9682M for 96 in camera 830 g mm Mosaic 2nd order and so on The available configurations are oh Tan Blaze Range Dispersion g m Ang Ang Ang mm 9682M 830M 4060 3500 5800 2 4 681M 830M 8125 5800 9900 4 8 2121 1200 5000 3600 6500 10 1 2121H 1200H 6000 5000 8500 10 1 2122 1200H 3000 3200 4000 5 0 4060 3500 6000 6 5 2 830 8125 6000 9900 13 1 a oO oO ol mn i Aen ee N 00 N wo i Oo vk ee 2 4000 3200 5000 17 9 H 7000 5000 9500 17 9 600H 3500 3200 4200 9 300 4200 3500 8000 Naina Exposure Exposure CCD min Photo min 682M oO N O
22. d counts 1 8 m TELESCOPE SPECTROGRAPH CONFIGURATIONS GRATING BLAZE DISPERSION EXPOSURE NAME g mm Angstroms Anstroms mm minutes 21181 1800 5000 fo 60 211218 1200 moo f5 Z Mo o 2161G 600 5000 fso 2 2161R 600 7500 30 lo 2131B 300 4200 60 10 2131R 300 6500 60 10 21 3 2 1 150 5000 120 56 Slits amp Image Slicers The slit or one of several image slicers is mounted by wing clamps at the Cassegrain focal plane to form the entrance 14 07 07 10 11 PM NRC HIA Dominion Astrophysical Observatory http www hia iha nre cnrc gc ca dao 185_e html aperture to the spectrograph The slit is adjustable from 0 001 inch 1 thou to wide open the width should be matched in microns to the resolution of the detector employed During conditions of poor seeing wider settings may be used to conserve speed although resolution will be sacrificed Typically a 1 5 slit is used which allows a comfortable oversampling with all the CCDs Note that the 0 8 slit with projected slitwidth of approximately 37 microns FWHM results in undersampling for the larger CCDs such as the SlTe 5 with 24 micron pixels 48 micron resolution 1 8 m TELESCOPE SLIT ADJUSTMENT SLIT WIDTH RESOLUTION AT FOCUS Thou Arcsec microns 10Ang mm 15Ang mm 30Ang mm 5 08 37 04Ang 06Ang 1 1Ang 7 1 1 50 0 5 Ang 0 8 Ang 1 5 Ang 10 h5 71 0 7Ang 1 1 Ang 2 1 Ang 13 20 92 0 9Ang 1 3Ang 2 7 Ang 19 30 13
23. d to the detector field sizes field verification is usually unnecessary hence the main use of the TV guider is indeed for guiding The offset from the center of the CCD field is fixed the guider position cannot be rotated or translated to aquire suitable guide stars The offset of center of the guider field on the sky is 18 2 arcmin west and 3 2 arcmin south of the center of the CCD or IR detector The autoguider is effective with guide stars as faint as m 15 but occasionally at high galactic latitude no suitable guide stars will be found within the 14 07 07 10 11 PM NRC HIA Dominion Astrophysical Observatory http www hia iha nre cnrc gc ca dao 185_e html 7 of 9 guider field For long exposures near the Galactic poles it is advisable to verify that guide stars are available before you come to the telescope See the Before You Come section below for how to do this The photometric capability of the system has been demonstrated to m 20 and may extend fainter if great care is exercised in sky subtraction When configured for CCD imaging a filter wheel holding four 50 x 50 mm filters up to 7 mm thick is mounted in front of the detector Alternatively three filters and one clear glass aperture so that the focus is not shifted may be used Johnson Cousins UBVRI filters are available Transformation coefficents to standard UBVRI values for our filter set depend on the choice of detector Approximate transformation coefficent v
24. da Council Canada de recherches Canada a a Frangus __ Cont Heip Search TS Home Centre of Sunrise NRC Site Library _ the Universe ESMEE Library EZITE List Sunset Interference Filters The table below provides a summary of interference filters currently available for use in the optical imaging camera of the 1 8 m telescope We will be adding detailed bandpass information as well as transmission curves in the near future For questions regarding specific filters please contact HIATelescopesupport nrc cnrc gc ca Observers may also request to use any of a set of narrow band 2 x 2 filters owned by Dr Chris Pritchet UVic Interested users should contact David Balam for additional information about the characteristics and availability of these filters Maximum transmission Central wavelength o A Bandwidth A Filter name 14 07 07 10 15 PM NRC HIA Dominion Astrophysical Observatory Filter iame wavelength A B blue 4238 V violet 5250 R red 5930 Johnson l infra red 7580 U in house 3550 G 9207 R Gunn V U B 4100 V 4700 Stroemgren Y 5500 U R Kron Cousins H Alpha 6564 Red cont 6650 Barr PK50 S II 6736 All Filters are 50 8mm square Published 2003 02 27 a 2 of 2 Central http www hia iha nrc cnre gc ca dao filters_e html Bandwidth Maximum A transmission 60 85 80 88 65 160 190 240 Important Notic
25. elescope Image Slicers Aperture Actual Designation bee Dimension Slit Width microns 1S32B 5000 13 5x25 h12 IS32R gt 5000 3 9 x 2 5 112 ISRVS lt 5000 3 8 x 5 6 250 IS96B lt 5000 5 2 x 1 4 62 Projected Projected Designation Width 32 Width 96 microns microns IS32B 20 36 IS32R 20 36 ISRVS 45 80 1596B 11 20 where the first number of the aperture dimension is the height in arcseconds As seen through the image slicer guiding eyepiece it appears as the narrow vertical dimension of the entrance aperture The relation Projected slit width Actual slit width x Camera focal length Collimator focal length 14 07 07 10 34 PM NRC HIA Dominion Astrophysical Observatory http www hia iha nre cnrc gc ca dao 12_e html 6of8 gives the tabulated projected slit widths for both 32 and 96 inch cameras Since the projected slit width should match the resolution i e two pixels of the detector the IS32 s are normally adequate for either camera and the IS32R should be used for all red configurations in any case Although the ISRVS is intended for use with the Radial Velocity Scanner the IS32B may be used in its place as this results in a significant reduction in guiding errors in velocity Image slicers greatly enhance the efficiency of coud observing as they effectively increase the slit width fourfold without loss of spectral resolution That is at the 5 6 arcsec per mm plate scale of this focus
26. es 14 07 07 10 15 PM NRC HIA Dominion Astrophysical Observatory lof8 i Herzberg Institute of Astrophysics DAO Homey About DAO gt Public Outreach gt Facilities v Telescopes 1 85 m Telescope 1 2 m Telescope gt Detectors Spectral Data Filters Information for Visiting Scientists Facilities Evaluation Form Observing at DAO gt Contact DAO gt http www hia iha nre cnre gce ca dao 12_e html National Research Conseil national Can da Council Canada de recherches Canada a a Frengaie__ Comtat Help Search Canada Site Home Centre of Sunrise NRC Site Library _ the Universe ECEE Library EZITE Sunset Dominion Astrophysical Observatory The 1 2 m Telescope and Spectrograph Technical questions You can e mail us at HIATelescopesupport nrc cnrc gc ca The spectrographs of the 1 2 m telescope are named in commemoration of Andrew McKellar 1910 1960 who in 1941 made the first measurement of the radiation temperature of the universe which became recognized in 1965 as the primodial cosmic microwave background a direct remnant of the cosmogenesis event The telescope itself is commonly referred to as the McKellar Telescope Overview The 1 2 m telescope was inaugurated in March 1962 and a new primary mirror was installed in April 1985 The current primary mirror is a low expansion borosilicate glass called Ohara E 6 its coefficient of thermal expansion is about two thirds that o
27. ewtonian Imaging Technical questions You can email us at HIATelescopesupport nrc cnrc gc ca This telescope is known as the Plaskett Telescope and since 1953 has held on its foundation pier a plaque commemorating John Stanley Plaskett The official naming of the telescope took place on June 4 1993 Overview The 1 85 m diameter parabolic primary mirror of the telescope feeds an f 5 light cone either onto a flat aluminum secondary to illuminate an imaging focus or alternatively onto a 0 5 m hyperbolic convex secondary to provide an f 18 Cassegrain focus where the spectrograph is mounted This telescope has seen considerable evolution since it went into operation on May 6 1918 and it is roughly true that only the tube and mounting remain from the original telescope The the all reflection Cassegrain spectrograph dates from 1967 the Cervit primary mirror was installed in 1974 and the f 5 modified Newtonian secondary and imager in 1991 The telescope encoders and control system are the products of the last decade Recent evolution of the telescope has been driven by user friendliness and safety considerations the original centrifugal governor clock drive has been retired from operation the dome shutters and windscreens are now activated by a remote control handset and most structures protruding from the rotating dome have been removed In late 1993 the telescope tube was enshrouded in a black canvas mantle to shield out stray light
28. f Pyrex During optical shop testing of the uncoated primary mirror in 1984 70 of the light was concentrated within 0 5 arcsecond 90 within 0 8 and 98 5 within 1 0 at prime focus Thus the mirror quality considerably excels over typical seeing limited image sizes obtainable at the DAQ site As with the 1 8 m telescope much effort in recent years has gone towards making the telescope and its instruments user friendly and relevant to the training of students The telescope and dome are under computer control from the ground level observer s room Automatic dome tracking is an added advantage for long exposures The 1 2 m telescope is normally used at the coud focus with high reflectance coatings for the second third fourth and fifth mirrors to optimize throughput The three mirror sets are Super Blue 3500 5300 A Aluminum 4500 A near IR and Gold 6500 A IR optics These mirror sets are rapidly interchangeable and self aligning so that it is possible to change from one set to another in about two minutes without the need to re centre on the star being observed The coud beam is f 145 after reflection from the hyperbolic secondary 14 07 07 10 34 PM NRC HIA Dominion Astrophysical Observatory http www hia iha nre cnrce gc ca dao 12_e html 2of8 third to fifth surfaces are flat while the coud spectrographs are designed to accept an f 30 beam so a lens located immediately following the fifth mirror converts the beam
29. ir spikes are usually quite recognizeable in the data being typically hundreds or thousands of electrons in intensity spread over only 1 3 adjoining pixels Thus they are easily removed during data reduction Cryogens The CCD detectors are mounted in Dewar flasks which must be refilled with liquid nitrogen at the start of the night and also in some cases during the night and when shutting down at dawn but not if another instrument is scheduled to go on the telescope that day The liquid nitrogen will be found in reserve flasks located on the observing floor near the 1 8 m telescope and in the coud chamber of the 1 2 m telescope These reserve Dewars should be pressurized to 10 pounds per square inch through a plastic hose connection from compressed nitrogen tanks in order to expedite filling of the detector Dewars from them As the CCD s are heated from liquid nitrogen temperature up to approx 110 degrees C in order to maintain charge transfer efficiency their Dewars require regular refilling typically about every 8 hours The CCD Dewars can be completely filled through a very narrow tube inserted inside a retaining tube which requires about twenty minutes When mounted on the 1 8 m Cassegrain spectrograph the orientation of the CCD Dewar is such that it can only be half filled in any case in this 14 07 07 10 13 PM NRC HIA Dominion Astrophysical Observatory http www hia iha nrc cnre gc ca dao detect_e html 4of5 situ
30. only that area of the detector which is illuminated by the spectrograph saving data storage space http www hia iha nrc cnre gc ca dao detect_e html 14 07 07 10 13 PM NRC HIA Dominion Astrophysical Observatory http www hia iha nre cnre gc ca dao detect_e html 30f 5 and readout time On chip binning permits pixels to be summed together in either the serial or parallel direction while keeping the read noise per sample the same This feature permits the sampling of larger areas of the detector without increased read noise but at the expense of spatial resolution and particularly cosmic ray noise resolution which can be a problem for longer exposures Note the values quoted in the table for dark current and full well are for unbinned pixels and will increase proportionally with bin size Cosmic Ray Events All silicon based detectors record the passage of cosmic ray muons which pass relatively unattenuated through the dome and detector housing However the bottom five kilometres of atmosphere does provide shielding equivalent to about a metre of lead at 5000 m altitude there is approximately 1 muon event per square mm per hour at sea level this rate is halved The rates also fluctuate with solar activity Thus in cosmic ray background low altitude sites such as DAO offer an appreciable advantage over higher observatory sites Still cosmic ray events will almost certainly be present on long exposures taken with a CCD The
31. pler shift of the star under refinements however One is that the masks are etched from copper on glass for maximum transmission Also the mask windows or slits are not parallel but are tilted slightly with respect to the line of dispersion By scanning the mask at a 45 degree angle in the focal surface the effect of the tilted lines is to stretch or shrink the mask to maintain proper registration at all velocities Currently there are spectral masks based on 14 07 07 10 34 PM NRC HIA Dominion Astrophysical Observatory http www hia iha nre cnre gc ca dao 12_e html T of 8 Procyon F5 for F stars on Arcturus K2 for G K and M spectral types and a carbon star mask for C type stars Thus the RVS is suitable for all stars cooler than about 7 000 K Following the mask sets of five superpositioning mirrors focus the transmitted light onto a photocathode whose small size permits minimal detector noise GEM This consists of an image rotating prism located just after the spectrograph slit in the coud room The two positions of the prism result in two images of the slit one inverted with five scans in one position of the prism followed by five scans in the inverted position thus if the star is de centred on the slit during this time the non uniform illumination will not result in a velocity like shift of the spectrum at the mask Also the RVS mask position is continously monitored by an encoder which is checked relative to the s
32. reduced or expanded program weather conditions bad or good will often modify your hopes of what is achievable during your observing run Have accurate coordinates the telescope control system will accept coordinates of any epoch a Prepare adequate finding charts for faint objects or crowded fields these are mandatory for service observing projects For ease of observing particularly for projects with many objects it is advantageous to write a file containing your program star list The format for such a list is straightforward for each object enter on one line the starname right ascension declination epoch and comments with spaces or tabs as delimitors between the fields If there is a space in the object name enclose the name in double quotes use colons and leading zeroes in the coordinate fields For example HD47129 06 32 02 4 06 13 10 1900 V 6 1 Plaskett s star Epsilon 2 Lyrae A 18 44 22 8 39 36 46 2000 B comp 2 3 away quad system Lines should not exceed 80 characters This file will permit acquisiton of the star by selecting within a Graphical User Interface GUI In order to transfer your file into the DAO computer network please contact an observing assistant In preparing for a run it may be wise to prepare charts for field verification or to verify that suitable guide stars are located in the TV guider field located 18 2 arcmin west 3 2 arcmin south of the detector field for the guider at Newtonian
33. s To Check Make sure the dome mode is AUTO This has the TCS maintain the dome opening in front of the telescope The dome mode is displayed near the top right of the screen Ensure that the telescope epoch above the telescope current position is the current date If entering coordinates by hand ensure that the correct epoch for the objects is displayed above the object coordinates See the command EPOCH Use use the command MOVE hh mm ss ss dd mm ss s If the target is in an available location the telescope should start moving at 10 slewing speed and the dome should start rotating Hold down the N button on the hand paddle This enables the telescope to slew at full speed Provided the telescope spectrograph isn t about to hit something wait until the telescope slows down and then release the N button In case of emergency telescope or spectrograph about to hit the North or South pier or clock case release the N button and press the Emergency Stop button on the top of the hand paddle If this unlikely event happens call the Assistant on duty When the telescope and dome status register On Target you are free to locate the object and start guiding The keypad keys 8 4 6 and 2 are used for guiding and the 5 key toggles the guide resolution which is displayed at the top right of the TCS terminal Facilities Auto precession Entered coordinates are precessed from the default or object
34. s of stars about 7 000 K or cooler The velocity range to be searched is adjustable within wide limits and the integrated signal is displayed in real time allowing the observer to proceed to the next star whenever the measurement quality reaches an acceptable level Wavelength calibrations for the spectrographs are provided by hollow cathode discharge lamps three are available Fe Ar as to avoid conflict with the stellar Fe lines and Th Ar Various configurations of lamp illuminations can be used for detector flat fielding depending on the spectral region and precision required Telescope Control System The telescope and dome operate under a Telescope Control operates from a terminal in the observer s room although both 14 07 07 10 34 PM NRC HIA Dominion Astrophysical Observatory http www hia iha nre cnre gc ca dao 12_e html 30f 8 telescope and dome can be moved under handset control from any specified epoch and the commands it accepts are almost identical to those used on the 1 8 m telescope The setting accuracy is currently about 15 over the whole sky but much more accurate over a restricted region of the sky The direct viewing coud field is only 3 diameter A TV viewer eases guiding on faint objects but is not usually necessary for m lt 10 The TV guider views either an area 3 1 x 2 4 in the field or else 1 2 x 0 9 around the image slicer aperture The telescope cannot collide with the dome nor with any ob
35. st spectroscopic and imaging projects Fiters 0N the telescopes They do have pixel to pixel sensitivity variations of the order of a few percent which can readily be calibrated and removed with flat field exposures on some uniformly bright source or for spectroscopic applications on some featureless continuum spectrum Detectors Information for Visiting Scientists Facilities Evaluation Form ObservingatDAO Several of our earlier CCDs RCA FA2048 PM512 SlTe 1 are nan permanently decommissioned while others such as the Tek 1 and Tek 2 may be occasionally used on an emergency basis At the present time the latter three of the four chips described below are usually available for mounting at the telescopes Contact DAO gt DAO CCD DETECTOR CHARACTERISTICS DESIGNATION UBC 1 SiTe 2 SiTe 4 SiTe 5 Manufacturer Loral SiTe STe SlTe Commissioned Sept 94 Dec 95 Mar 00 June 98 Type Thick Thin Mhin fhin Illumination From a Backside Backside Cosmetics Good P24 V Good V Good oo column Goo Goo 5 iif pixels 4096x200 1752x532 4096x2048 1024x1024 alli 1 15 24 size microns lof5 14 07 07 10 13 PM BGU NRC HIA Dominion Astrophysical Observatory 2 of 5 DESIGNATION UBC 1 SITe 2 SITe 4 SiTe 5 Chip size mm peen e Readout noise e pP x oo fo N O O xX fe O O _ pP x wo O N N DA SJ o x lt N gt A ol foe 2 are e Dark current e m
36. structions on the observing floor with the sole exception of the ladder if it is improperly stowed The polar axis is rotatable through more than one complete rotation but is ultimately limited in travel by the cabling to the telescope In the normal position with the telescope tube east of the pier at the meridian the limits in hour angle are 7 7 hours east to 20 hours west If you plan to monitor a circumpolar object from say 9 hours east through 3 hours east you can still do so without encountering these limits by reversing the telescope This is done by driving the telescope through the north pole and setting on a readout right ascension offset 12 hours from the desired coordinate In this case the hour angle range which is attainable is also offset by 12 hours viz 19 7 hours east through 8 hours west Note there is also a limit switch in altitude which will cut off the telescope drive at 8 degrees above the horizon The above limits suggest that the entire sky above 8 degrees altitude is accessible to the telescope This is not really achievable in practice as trees obscure the eastern and southern horizons to as high as approx 20 degrees altitude in some directions A practical limit in declination near the meridian is thus about 30 degrees Spectrograph Configurations amp Exposure Times The coud spectrograph optics are described in detail by E H Richardson in JRASC 62 313 1968 Basically there are two separate spe
37. tepper motor position if any discrepancies or discontinuities occur an on screen warning is sent to the observer Repeated scans over a preselected velocity range are summed to remove seeing and transmission fluctuations and displayed on an oscilloscope screen When a well defined minimum is visible the observer can interrupt the scan to compute a velocity Generally a two minute integration yields precise velocities for magnitudes B lt 9 somewhat longer integrations approx 30 minutes extend the observable range as faint as approx B 15 Since the Telescope Control System TCS can acquire a star typically in one or two minutes this means it is quite feasible to observe about fifteen stars per hour magnitude whose velocities are approximately known For stars whose velocity is quite unknown it usually takes some time to locate the velocity dip On line data reduction yields heliocentric radial velocities with a precision of about 0 2 0 3 km per second these require only small zero point corrections from a hollow cathode arc and standard velocity stars to become publishable velocities The velocity dip profiles which area This permits more sophisticated data reduction later if needed in most cases this is necessary only for double lined spectroscopic systems of small velocity separation which display a blended velocity minimum For further information on the Radial Velocity Scanner see a Fletcher Harris McClure amp S
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