TCP`s user manual – Real Time Photometry (RTP)
Contents
1. Real Time Photometry RTP 20 09 2011 RTP must be started with the f lt flatstr gt option The flat fields that match the query will be averaged normalised and saved as Flat fits in the working directory This file will be used next time RIP is run unless a specific filename or query string is given RTP can be started and stopped at any point during or after the observation run When it is started it will get the flat field and prepare the Output data files ohot raw and phot dat before searching for input CCD fits files in the data directory It will immediately process all the files it finds and then go into a delayed loop where it will process files as they arrive RTP can also be used for simple processing of the data after the original session is over Then it can sometimes be useful to have a delay between the processing of the images to monitor the progress This can be done by calling RIP with the d lt delay gt option where the delay time is given in seconds and can be a floating point number To start RTP just write gt rtp parameter1 argument parameter2 argument The RTP front page will appear See Figure 1 This page lists the most used options for RTP and has been designed so that the keystrokes used to set the parameters are the same as those used for the processing flags on the command line So this page works both as a reminder and a way to check the input parameters before the processing2. Command line options d delay Include a delay in seconds between each processed frame Default is no delay f flat files Filename base for flat fields Default is flat fits log file Filename for log file Default is rtp og m nsigma Median filter sky annulus values rejecting values that lie more than nsigma times the standard deviation away from the mean value r aperture radius Xx aperture x position y aperture x position s sky annulus Use sky annulus to correct for sky level Annulus is all pixels outside the given radius TCP s user manual Real Time Photometry RTP 20 09 2011 F Compute the Fourier transform of the light curves Produce the file ohot sft J O Activates the offsets for the stars M Activates the Moving Average Photometry MAP option i number of iterations Set the number of iterations used to compute offsets and MAP C Compute the centroid values S Display apertures in Saoimage R Reprocess all data W Use weighted sums when computing aperture values
3. TCP S USER MANUAL REAL TIME PHOTOMETRY RTP Last modified 2011 09 20 This version by Jorge Garcia April 2010 Original version by Jose M Gonzalez June 2007 Send comments and suggestions to Jorge Garcia jogarcia AT iac es Or to the Support Astronomer Group ttnn _a AT iac es TCP s user manual Real Time Photometry RTP 20 09 2011 1 INTRODUCTION CCD images normally require a lot of calibration work to be rendered useful for high precision photometry It is therefore not unusual to spend considerable time processing the data before accurate photometric magnitudes are obtained Time series photometry requires additional steps to produce differential photometry that can be subjected to Fourier analysis to reveal faint periodic modulations A requirement for the TCP Tr amso CCD Photometer was that light curves of the targets could be produced in real time so that the observer can investigate the results as they arrive The real time photometry RTP is performed by using the window definition files johotwins dat and ohotwccd dat to convert the CCD pixel data written by the acquisition program to aperture images for pre processing The flat field images are converted to a window list format by extracting the proper areas using the information in the file ohotwins dat During processing each observation frame will be divided by the appropriate flat field window A bias level value is computed from the l
4. ast window in the raw CCD image if there is information about such a window in the file johotwccd dat Each CCD window is flat fielded and bias level subtracted before the aperture sums are computed 1 1 How does RTP work RTP uses circular apertures with an arbitrary centre and radius within the aperture windows when computing the total flux inside the windows It is important to remember that the first few columns read from the CCD is useless In particular the pixel read in a line is always zero the next pixel has a somewhat high level and then the amplifier gives progressively more stable output as more pixels are read in sequence The default setup avoids the first four columns using an aperture mask with a radius of 30 pixels centred at pixel 34 30 The aperture can be set from the command line with the r lt radius gt x lt xcenter gt y lt ycenter gt options RTP can also use an automatic centring algorithm This computes a simple geometric centre of gravity within the aperture and re centres the aperture iteratively The centring algorithm is specified on the command line when RTP is started The option O will compute initial offsets for each stars and the M option will invoke the Moving Aperture Photometry MAP mode computing a new aperture centre for each frame For both option the lt num gt parameter can be given to specify the number of iterations desired Sky subtracted photometry values are compute
5. d either by using the value from the last sky channel aperture or by using a sky annulus around each aperture This last option is accomplished by invoking RTP with the s lt rad gt parameter The quantity lt rad gt gives the number of pixels along each edge to be used The first four rows in the image are avoided TCP s user manual Real Time Photometry RTP 20 09 2011 Differential photometry is computed for the target channel 1 and each reference stars If more than two reference stars are available differential photometry is computed between them so that any periodic variability in the reference stars can be easily checked If possible a differential photometry value is also given for the target relative to the sum of all the reference stars which is useful in fields where all reference stars are significantly fainter than the target These data are continuously appended to three separate photometry files ohot raw ohot dat and phot dif as soon as each new integration has been received and stored by the acquisition programs Qicp or tcocom While waiting for new data to arrive RTP calls gnuplot to show plots of the photometry files so that the observer can analyse the light curves In addition RTP can show the Fourier transforms of the photometry files as the observations are being made This gives opportunity to the observer to inspect the data in real time being e g really useful for programs t
6. is started One new command line option has been added G will inhibit the display of the start up screen and cause RIP to commence processing immediately G is also the command in the front page menu to give the system the Go signal The basic keystrokes you have to check always are r and s which control the radius and the sky annulus region for each aperture respectively TCP s user manual Real Time Photometry RTP 20 09 2011 Data filename format Number of first data file Radius of fitting aperture Sky annulus region pixels Sky field number to use Number of sky data fields Name of flat field images Object name Moving aperture photometry MAP Number of iterations for MAP Offsets of individual apertures Times from FITS headers Differential photometry mode Go RTP Quit Startup Menu Change setup or hit to start processing J Figure 1 RTP program front page Example gt to r 15 s 10 This example selects a radius of 15 pixels for the aperture photometry and performs the sky subtraction with the sky annulus option using a ring of 10 pixels This also can be done by typing only RTP and then on the RTP front page using the r and s keystrokes Then after hitting G the following screen appears TCP s user manual Real Time Photometry RTP 20 09 2011 S O observera tccd Data_Jose AMCVn_March04_IAC80 AMCVn_21_3 Red Terminal KW FU EQ RIP real time proces
7. rying to detect new variable stars 2 WORKING WITH RTP a To process data with RTP is necessary to previously set up a working directory Making a directory at any desired path and creating a symbolic link in this directory to the actual directory containing the data do this When real time photometry is being done a directory to keep the processed data must be created so that existing files are not overwritten A link must be made to the data directory where Qtcp15 or tcocom stores the incoming CCD frames For instance if Qtco15 is saving images at home observer 1805072030 data the following actions must be done gt cd home observer 1805072030 gt mkdir RedB if you want to reduce B images gt cd RedB gt In s data 1 data NOTE Be sure that you have copied the files phot to the data directory b If flat field processing of the data is required then another symbolic link named flats to the data directory containing the correct flat field images should be made You have previously stored the flats with the separator program It can be the same as the previous data directory As an example for filter B flats gt In s flat 1 flats Note the first time it appears written flat and then flats RTP will then sum all fits files in the flats directory having names matching the default string flat fits To specify another query string for the flat fields c d TCP s user manual
8. sing Version 1 30 Roy H stensen 1999 2002 Displaying Plot type Data style Log scale Autoscale Window size Aperture radius Aperture center Raw data phot raw Full plot Lines Off On 64x64 pixels 15 00 pixels area 706 86 34 00 32 00 outside r 22 pixels npix 27390 data 0 X filter el FF Next data file data wO0O000 fits Figure 2 RTP program information panel running The number keys indicated in red will toggle on and off which channels to display e Changing the display When RTP runs it displays through gnuplot the propagating light curve see Figure 3 The d key switches from raw data Figure 3 and processed data data with sky subtraction and differential photometry see Figure 4 whilst the F key displays the Fourier transform of the light curves see Figure 5 To go back to the light curves is necessary to press d again The centroid file generated as before and written to ohot cen can be plotted in real time aiding the observer in keeping track of the accuracy of the telescope guiding The ohot cen file is plotted in the same way as the photometry files upon pressing the C key To switch on off plot channels just press the corresponding channel number Coumta AH ree 000 Bonn PA aye ae UN VN oie Pa aaa PROT Gnur lot chal A pA N eaen cee oe eos Figure 3 RTP displaying light curves ra
9. w data in real time TCP s user manual Real Time Photometry RTP 20 09 2011 Eg me ES uy amp Nis Figure 5 RTP displaying the Fourier Transform f Producing plots lt is possible to save the currently displayed plot as a postscript file with the P key The filename will be rto ot ps TCP s user manual Real Time Photometry RTP 20 09 2011 Sr a ot APPENDIX LIST OF COMMANDS To display the list of keystroke commands while running RTP the key must be used The following display will appear amp 4 observer tccd Data_Jose AMCVn_March04_IAC80 AMCVn_21_3 Red Terminal K W ryt Keystroke commands Plot Raw Sky or Processed data Plot full or ranged plot Plot channel toggle Plot channel 1 ALL toggle Plot sky channel toggle Plot aperture centroids Calculate and plot FT Plot next filter in sequence Toggle autoscale on off i Fold lightcurve every seconds Hk Increase or Decrease fold range Make PostScript plot rtplot ps Make LaTeX plot rtplot tex Bigger or smaller aperture Move aperture left or right Move aperture down or up Plot style toggle lines points Logaritmic scale plot toggle Reprocess all data M Make new Mask mask fits Set object name for saveplots Test image testview fits Quit This help page S C f P S R 0 q Press a key to continue J Figure 6 RTP keystroke commands
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