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C100/RetroCam Observing Procedures

Last update for this manual to be used on the C100 telescope on July 18th, 2011



1. Initialize System

  • Field of view is now: ˜ 3.4' arcmin

1.1 Instrument Control Computer: ARACHNE/CSP5 (Windows XP)

  • User name: cspuser
  • Password:
  • Double click on the RetroCam icon.
  • A window called Database Initialization pops up:
    • Check Camera, Telescope, Guider, and FilterWheel ar all ONLNE.
    • TemperatureControl should be OFF.
    • Type in observer's name in Observer.
    • Then click OK
  • A window called RetroCam-Control pops up.
  • Go to the Modules tab and open the TeleGUI and, Display. Once you open TeleGUI the UT time updates.
  • In Telescope Control window go to the File tab and open SkyMap, Airmass, and ObjectList.
  • In RetroCam-Control window go to the Option tab and select DataPath.
  • In the window that pops up write the directory in csp4 where the data will be directed. Use the CSP naming convention.

    We are currently using Rigel as Data Reduction Computer, thus 'datapath' needs to be defined accordingly. Check on next section (1.2.1) for details. 
  • 1.2 Data Reduction Computer

  •  1.2.1 Rigel

  • User name: retrocam
  • Password: check on control room or ask the technical staff
  • After logging in, type: 'goiraf' on a terminal in Rigel. This will open an xgterm and a DS9 window, and start an IRAF session.
  • The quick-look reduction package will load while IRAF starts.
  • On a terminal in Rigel  type  'cd /Volumes/Data_Rigel/'
  • Create the working directory for the night: mkdir 20111107_08  (for example)
  • Specify the working directory under 'Data-Path' on the RetroCam control window in CSP5: \\rigel\Data_Rigel\20111107_08
  • If desired, you can run  RetroCam from Rigel using VNC (so you don't need to type into CSP5). Ask the technical staff for help if you are interested in trying this option.
  • 1.2.2  Alternatively you can use csp4 (Linux)

    • User name: cspuser
    • Password: available on the telescope
    • Open a terminal (you can use the icon in the task bar).
    • Create a directory for the night and make it writable by csp5. For the example above:
      > cd /data
      > mkdir 20050906_07
      > chmod 777 20050906_07
    • Open an IRAF window by clicking on the "drawer" icon in the task bar.
      Or in the terminal, type:
      > cd
      > xgterm -sb -e cl &
    • In the IRAF terminal, go to the data directory, e.g.:
      cl> cd /data/20050906_07
    • See the use of observing scripts in Section 4 below.
    • Open DS9 from the Linux terminal:
      > ds9 &
    • set Data-Path on CSP5 RetroCam control window accordingly (the tehcnical staff can assist you with this).

    1.3 Check UT time

    • Check the current UT time (e.g, the USNO web page).
    • If the Universal Time at the TCC-Guider PC differs from this more than a few seconds, ask the telescope operator or the daytime technitian to try fixing it.
    • It is very important that you check the UT and ST are right (within some seconds) in the Retrocam-Control window in csp5.
    • If this is not the case, restart the RetroCam control program in csp5 as described in Section 1.1.
    • Once you re-open the TeleGUI module the UT should update and be close to the time in the TCC-Guider PC.


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2. Calibrations and Telescope Setup

    2.1 Dome Flats

    • Ask the operator to set the telescope for dome flats
    • In Retrocam-Control window set:
      • Exptime = 5
      • Readmode = Double
      • ObjType = dflat
      • Loops = 15
      • Object = Domeflat 
    • Turn ON quartz light (max voltage is 480).
      • Y:  335
      • J:  295
      • H: 265
      This way you should get about 12,000 ADU on average.
    • In Retrocam-Control window select a filter and click the Go button to start a loop of flats.
    • When done, turn OFF quartz light.
    • Click Go again to get "lamp-off" flats.
    • Change filter and lamp level, and repeat the two previous steps.
    • When the sequence of dome flats is complete, check that the quartz lamp is OFF.

    2.2 Sky Flats

    • Ask the operator to go to an empty field or just try pointing to Zenith if it is still  clear. Beware that some of the empty fields are dark clouds in the Milky Way which contain plenty of stars in the NIR. 
    • In Telescope Control window set dy = 10 (10 arcsec steps).
    • In RetroCam-Control window set:
      • Exptime = 5
      • Readmode = Double
      • ObjType = tflat
      • Filter = Hc
      • Loops = 1 or 2
      • Object = Skyflat 
    • Start a test exposure with Go. Repeat until you have gone down below 20,000 ADU. Make sure that average counts are indeed going dwon between subsequent integrations. If not, the chip is still saturating.
    • Change Exptime = 5.
    • Reset counter in Filename to first unused number you had before the tests.
    • Push Go to start the first flat.
    • Push the N or S buttons in Telescope Control window between exposures.
    • Alternatively, you can do the offsets by running a dither macro: In RetroCam-Control window press Dither and select
      • Dither-Pattern = rot-5
      • Dither-Step = 15
      • Guider = none
      You can change the exposure time while the telescope offsets between integrations.
    • Take at least five (5) images.
    • Change Filter to Jo and repeat the procedure above.
    • Take at least 5 images with 8,000 to 20,000 ADU, and offsetting the telescope between them.
    • Finally, go to Filter = Yc 
    • If you don't get enough counts you can ask the TO to move the telescope  West 1h or 1.5h to increase the illumination.

    2.3 Telescope Zero-Point (CSET)

    • Ask the operator to point to a bright star for the zero-point
    • In RetroCam-Control window set:
      • Exptime = 3
      • Readmode = Double
      • ObjType = test
      • Filter = Yc
      • Loops = 1
      • Object = Test
    • Take an image with Go.
    • In the Display window click on the center of the bright star.
    • In the same window click on Center Telescope.
    • In Telescope Control window click on the 0,0 button.
      The telescope will now center the bright star.
    • Ask the operator to do the 'CSET'.

    2.4 Telescope Focus

    •  The first estimate for the focus values with a T=8-9 gives a first offset of +0.15 units higher than Y-H. E.G.: first focus for Y-H=43.00; J=43.15 on July 18th 2011. A focus sequence is needed at the beginning of each night and sometimes during the night also. The image quality needs to be monitored along each observing sequence.
    • If the focus is fairly good, ask te operator to start a sequence, take a single 10sec image, and wait for the operator to change the focus value
      • Exptime = 10
      • Filter = Yc
      • Loops = 1
      • ObjType = test
      • Object = Test,
    • Display the images in csp4 and run imexamine and its commands 'r' and 'e' to see the size and shape of point-like sources.
    • Tell the operator what the best focus was so that he does an fset.

    2.5 Darks

      Darks may be taken in the afternoon if the temperature is not much higher than the expected one for the night.
      Else, they should be taken in the morning, or during the night in case no object can be observed.
      Darks should be taken every night with each exposure time used that night.
      Therefore, you may need to add darks in the morning, once you know which exposure times you have used.
      Note that this includes all the exposure times used for twilight flats.

    • In the RetroCam-Control window select:
      • Readmode = Double
      • ObjType = dark
      • Filter = dk
      • Loops = 15
      • Object = Dark
    • Set one of the required exposure times in ExpTime.
    • Click Go to start taking the darks.
    • Repeat with every required ExpTime.


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3. Observing

    3.1 Science targets

    • If you have an  Object List  already in CSP5 just open it in a window going to File and Load
    • You can use the buttons to Add, Edit, or Remove an object and also editing a new object list.
    • Remember to save your changes or else you'll lose them when you close the application.
    • The Preview button shows the situation of the selected target in the Airmass and the Skymap windows without having to point the telescope to the object.
    • The SendTo button is now working for sending the target coordinates to the TCS.
    • Select an object and send it for the operator to move the telescope to the target.
    • When the slew is complete, press the Get button in the Telescope Control window in order to have the right coordinates RA and DEC written in the image headers.
    • To check the pointing, in the RetroCam-Control window set:
      • Filter = Yc or Jo
      • Exptime = 10
      • Loop = 1
      • ObjType = astro
      • Object =   name will be automatically loaded from the Object List
    • Take a test image by clicking on Go.
    • If you need to correct the pointing, use the dx and dy offsets and the directions panel in the Telescope Control window.
    • The upper-left (NE) quadrant should be avoided because it contains several dead spots.
    • Reset the Filename counter to the value previous to the test (unless you want to keep those), and set Exptime, Loops, and Macro.
    • To define the Macro, press Dither and select the options of Dither-Step, Dither-Pattern, and Guider. Make sure you select Guider = auto.
    • Ask the TO to start guiding.
    • Start a dither sequence by pressing Execute in the RetroCam-Control window.
    • Also remember to apply the focus offset when you change from/to J.
    • You can make use of the quick-processing scripts described in Section 4 below to check the quality of the data and perform quick photometry, and adjust exposure times or dither sequences.

    3.2 Standard Stars

    • If the night is photometric, you may want to observe at least 3 or 4 Persson Standard stars.
    • In the Object List window go to File and Load.
    • Select the file persson.objects and click Open.
    • The list of Persson standards is displayed.
    • Select a standard from the object list and SendTo the TCS, and tell the operator to slew.
    • In the RetroCam-Control window select:
      • Exptime between 5 
      • Readmode = Double
      • ObjType = standard
      • Loops = 1
      • Object = SJ####   
    • Take a test exposure with Go and check the field and exposure time.
    • You may need to move the star off the quadrant divisions. If so, in Telescope Control set dx and dy to something like 50 and move diagonally in the chip. This offset should be now smaller. Try with smaller offsets and cross-check.
    • Avoid the upper-left (NE) quadrant. It cointains spots of dead pixels.
    • If the star is too bright, you may need to defocus slightly the telescope so that it doesn't saturate.
    • In the RetroCam-Control window select the macro by clicking on the Dither button. Then select:
      • Dither-Step = 15''
      • Dither-Pattern = rot-5
      • Guider = none
    • No guiding is required.
    • Launch a dither sequence by clicking on the Execute button.
    • Change filter and repeat the previous step until you have done Yc, Jo and Hc.
    • Remember to apply the focus offset when changing from Y-H to J.

    3.3 Guiding

    • Guiding is  done automatically by the telescope. Once you're pointing to your target, when selecting the macro on the Dither, choose guider=auto.
      Then the telescope operator will search for a guide star and put it into the guiding box and shall start guiding, and when ready, the observations can start
    • A  SkyMap is available. The TO may use it to find guide stars.


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4. Quick-Processing IRAF Scripts

  • A series of IRAF scripts are available in Rigel and csp4 to help the observations.
  • The scripts are loaded automatically when you start IRAF. The task definitions are given in the '' file in ~/iraf/.
  • The script files themselves sit in ~/iraf/retro_quick/.
  • The following tasks are available:
    • dis:
      Displays an image without having to type in the whole name.
      Usage:    cl>  dis  num   loo
      where 'num' is the frame number, and loo is the loop number.
    • disi:
      The same as above but it starts imexamine.
      Usage:    cl>  disi  num   loo
    • dp:
      Displays the difference between two "_001" frames.
      Usage:    cl>  dp  num1   num2
      where 'num1' and 'num2' are the frame numbers of the images to be subtracted.
    • pdiffi:
      Displays the difference between any loop of two frames and starts imexamine.
      Usage:    cl>  pdiffi  num1  num2
      by default, it subtracts loops "_001" of both frames.
      You can edit the optional parameters 'l1' and 'l2' to use other loops.
    • avgo:
      Displays the difference of two frames after averaging all the loops in each one.
      Usage:    cl>  avgo  num1  num2
      You can modify the optional parameter 'scl' to change the scaling factor to be applied before subtraction --- scl = "mode" is the default.
    • sky_stats:
      Shows the median and mean sky level for a range of frames. Useful to check flats.
      Usage:    cl>  sky_stats  num1  num2
      where 'num1' and 'num2' give the range of frames to analyze.
    • p_fid:
      Mark a fiducial star used to align dithered images.
      Usage:    cl>  p_fid  r  num1  num2  aut/man
      where 'num1' and 'num2' give the range of frames in a sequence. Options 'aut' or 'man' allow to make the program select a star, or the user to mark it. The task will write the star position in the headers of frame num1.
    • p_fx_asecs:
      Correct the RA and DEC offsets between frames that are written in the header keywords ASECS and DSECS.
      Usage:    cl>  p_fx_asecs  r  num1  num2
      where 'num1' and 'num2' give the range of frames in a dither sequence. The user will be prompted to mark the same star in all frames (after averaging the loops). r_quick will usually fail if this is not done in advance.
    • p_mimdel:
      Delete a range of frames of some kind.
      Usage:    cl>  p_mimdel  pre  num1  num2
      where 'pre' is a frame prefix ('icr' for loop-combined, 'isx' for sky-subtracted, etc.), and 'num1' and 'num2' give the range of frames in a dither sequence. Since p_fx_asecs fixes the headers of 'irr' frames only, you will need to delete the 'icr' frames before running r_quick, in order to get the right offsets.
    • r_quick:
      Produce a quick and dirty stack of a range of frames.
      Usage:    cl>  r_quick  num1  num2
      It produces a sky by averaging the frames. It asks the user to mark a few stars with 'a' in imexamine. It may fail if the dither steps are too large (>30''), or if the guider star got lost..
  • To make a fast combination of a dither sequence:
  • rcmosaic: For example, for a sequence of frames 10 to 18  type: 'rcmosaic 10 18' and follow the instructions that will be displayed. You can also go step by step as follows:
  • p_fid r 10 18 aut
  • p_fx_asecs r 10 18
  • p_mimdel icr 10 18
  • r_quick 10 18

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Last modiied on August 28, 2011 by Nidia Morrell (


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