C40/CCD Observing Procedures

Last modified on May 26, 2012 (Nidia)

IMPORTANT: START BY CHECKING THAT WE HAVE THE RIGHT FILTERS IN THE CAMERA:
LC-3013 (B), LC-9844 (V), u', g', r', i'

Initializing systems

• 1. Update UT in DATA PC (located in light blue rack)
  • Please update the UT Time in the data PC. For this, you need to open
    a terminal on Puma and telnet to the data PC, in this way:
  • Telnet pc
  • user name: root
  • password: available at control room
  • date -z0
  • date -d0
  • date yyyymmddhhmm.ss
  • exit
  • Type 'date yyyymmddhhmm.ss'
  • Type 'date' (to confirm entry)
  • Type 'exit' (to exit from data pc)
  • Current UT can be obtained from several sites, like this one
  
  
• 2. Update UT in TCS computer
  • In TCS computer you need to type 'UT hh mm ss' followed by RETURN
  • Check in the screen that the UT was properly changed
  
  
• 3. Start CCD Control Window in Data Acquisition Computer (Puma)
  • login: obs40a or obs40b
  • password: check label on monitor
  • cd DATA
  • mkdir SWO_DC_20111124_25 (e.g.)
  • cd SWO_DC_20111124_25
  • cp ~/csp/filter.names ~/csp/subraster ~/csp/ccd.macros (or edit file with 6 filter names using "ugriBV" IDs)
  • ccd (opens CCD control window)
  • before the CCD control window appears you have to select 5 parameters from the menu:
    • Curtain
    • Site3
    • 32
    • LCO-40
    • LCO-40
  • On the CCD control window select Gain 3
  • On the CCD control window select Subraster and enter the following values
    • 810 2010
    • 1 1201
    • Click Apply
    • Click Done
  • Open an IRAF window and change to the recently created directory (20020914_15)
  • Open DS9 window
  • Check the display size in IRAF, and adjust it accordingly to the data size:
  • show stdimage
  • set stdimage=imt4096 (4096 display is good to examine focus images; then you can use 2048).
  
  
• 4. Activate Telescope
  • Turn console ON (rotate key)
  • Turn Power ON
  • Check that platform is clear and on TCS computer, type 'COVER' (telescope will slew south)
  • Go to the platform, raise platform, and remove the telescope cover
  • Lower platform
  
  
• 5. Initiate Guider
  • Bring telescope to the zenith by typing ZENITH on the TCS PC (the system will ask you to confirm that the platfomr is down)
  • From any window in Puma computer type command 'rgdr', which will open guider window
  • A new window will appear where you need to enter -161 in X box and 1412 in Y box (next to GOTO box)
  • Click GOTO and SETCENTER
  • Click PARK before taking calibrations (PARK position is X = 0, Y = -558)
    NOTE: GUIDER SHOULD ALWAYS BE AT THE PARK POSITION FOR TAKING CALIBRATIONS AND NEAR IT FOR THE OBSEVATIONS

Calibrations

• Turn OFF platform lights from console
• From the focus control (small silver box next to PUMA monitor) set focus value to ~22.000 (upward) before taking flats.
• Slew telescope to HA= 03:07:00 E, DEC= -25:00:00, and rotate the dome to the encoder reading 7834 (you can do this either moving the dome from the console or typing DOME 282 on the TCS computer). This will set the telescope pointing to the flat field screen. To save time, you can type DOMEFLAT which will reach nearly the right HA but not the DEC. You then need to type in the current value or RA (adding ~1 minute) and DEC -25 00 00, and SLEW to that position. Small adjustements, if needed, can be done with the hand paddle.
• Turn ON quartz light from grey box over lightblue rack and adjust voltage to ~930 units (check with one integration in g 30s).
• Check that lamps are pointing to the white screen and make sure that the illumination of the screen is truly uniform
• In 'ccd' window set exposure time, filter, Loop to 7, Imtype to flat, and object to "Domeflat"
• Exposure times:
  • g': 30 sec (~12000 cts/pixel)
  • r': 7 sec (~12000 cts/pixel)
  • i': 5 sec (~15000 cts/pixel)
  • B: 120 sec (~11000 cts/pixel)
  • V: 25 sec (~12000 cts/pixel)
• Start sequence with START botton
• It is possible to take the whole sequence of flats with one click. You need to have the file ccd.macros in the current directory.
  Type "doflat" in the MACRO box in the 'ccd' window and click "RUN MACRO".
• When the sequence of flats is complete turn OFF quartz lamp on grey box
• In 'ccd' window set exposure time to 0, Loop to 10, Imtype to zero, and object to "Bias"
• Start sequence with START botton

Opening dome, and Preparing Telescope Control System (TCS)

Before sunset you must do the following:


• Turn ON fans in adjacent room (turn ON switch and set reostat near maximum value)
• Push OBTURADOR on console to open shutter
• Push ASENCION RECTA on console to turn ON tracking
• Go up to the telescope to lower the wind screen (from small silver box labeled 'UP' and 'DOWN') on left side of the pillar.
• In TCC-Guider PC, type 'DOME AUTO' to activate dome rotation
• In TCC-Guider PC, type 'TP' to activate telescope pointing model (this is not necessary if the model is
  already activated since this is a toggle key;
  check on the TCS screen if the 'TP' flag is on, TP should be highlighted in green, TP)
• In TCC-Guider PC, type 'MP 2011.5' to set the coordinate epoch (for pointing to bright star ONLY)
• Turn on power of guiding camera in lightblue rack, and turn OFF 'bright' button

Skyflats

At sunset you must begin taking sky flats:


• SLEW telescope 1 or 1.5 h East
• Type DOME AUTO
• In TCC-Guider PC, type DBB 20, (set step to 20 arcsec)
• In 'ccd' window set exptime to 3 (minimum), choose u' filter, set Imtype to flat, and object to "Skyflat"
• Start exposure with START botton
• After completing the exposure in TCC-Guider PC, type SS to slew telescope south by 20 arcsec
• Take 5 frames per filter with exposures longer than 5 sec and never exceeding 18000 adu.

Telescope Zero-Point

• In TCS PC, type RA hh mm ss.ss, and DEC dd mm ss (ccordinates of a bright star near the zenith)
• In TCS PC, use the SLEW command to slew the telescope to the desired position
• Take a short (3s) exposure and determine the offsets in X and Y (pixels) to be applied in order to have the bright star in the center of the image. Offsets in RA and DEC will be .435" * X and Y, respectively. To apply these offsets, use the commands RBB and DBB in TCC (but be aware that RBB is inverted in sign, thus to move the telescope E, for example, you need to type W). To move in only one direction, you need to type it twice, e.g. RBB 20, then EE, will move the telescope 20 arcsecs W.
• Here's an example:
• The images will have N down and E left (as labeled on one of PUMA's monitors -the one on the right).
• We need our field approximately centered on XY 600,600 on the image. Thus, if the pointing star is in x = 200 y = 600 you need to move 400 pixels E, which is 400 * .435 = 87 arcsecs. As the command RBB will reverse the direction, you should type:
• RBB 87
• WW
• Take a new exposure to check that the offset worked fine, and compute a new correction if not.
• Once you are happy, in TCS PC, type CSET to zero-point the telescope
• You should see the bright star in the guider field of view by clickig CENTERFIELD on the GDR window.
• If the star is far from the cross, use the GDR keypad to bring the star to the center, and then click SETCENTER
• Do not forget to click PARK before starting observations.
• To focus the guide camera, there is a switch labeled as Focus + - above the CCD electonics unit (in the light blue rack).

Focusing the Telescope

• Point to a 10th magnitude star
• Click PARK in 'gdr' window
• In 'ccd' window click OFF next to subraster (the full CCD will be read), set exptime to 10, Loop to 7, filter=V
• Use focus bottons to set focus reading to 0 in box located above console (always moving upward)
• In 'ccd' window click FOCUS to start first exposure of 10 seconds
• Once the first exposure is complete increase focus by .05 units and click on FOCUS again.
• Complete sequence of 7 exposures
• In IRAF window display image 'focus'
• On console set the focus to the best value
• Don't forget to enable the subraster in the 'ccd' window (click ON)
• Focus Offsets are provided in the next table:
  
  

  u	-0.45
  g	-0.45
  r	-0.45
  i	-0.45
  V	0.00
  B	+0.08

  
  
  
  
  
  
  
  
  
• Focus values reference: last focus value on Oct. 29 2011, with T = 13, focus for u-g-r-i= 21.575. Decreasing T, decrease focus too, aproximately with 1 degree of T, 0.05 units

Using the guider

• In 'gdr' window you need to enter -161 in X box and 1453 in Y box (next to GOTO box)
• Click GOTO (wait a few seconds) and click SETCENTER
• Use TCC to SLEW telescope to your target
• In 'gdr' window click PARK to remove guider from the field of view of the CCD
• In 'gdr' window turn ON the KEYPAD and use arrows to move the guider around until you find a guiding star
• In "GUIDER" enter the parameters of the camera (check sheet)
• On the TCS keyboard you can use the arrows to move the white box and put it on the guiding star
  (if the box doesn't move type 'xy5')
• On the TCS use F3 to activate guider
• On the TCS use F1 to de-activate guider
  
  

Observing

• In 'ccd' window set Imtype to object, select exptime, and filter
• Check exposure times here.
• Don't forget to apply focus offset for the selected filter
  • u': -0.45
  • g': -0.45
  • r': -0.45
  • i': -0.45
  • B: +0.08
  • V: 0.00
• Turn ON guider (F3)
• In 'ccd' window use START to begin exposure
• Turn OFF guider (F1)
  

WARNING: Sometimes it may happen that a slew gets aborted, with a "Slew correction too large! Slew aborted!" message issued to the 'System Messages' window in the TCS screen. A new SLEW will send the telescope to the desired position, but you must type also DOME AUTO in order to reset the dome motion, otherwise it will get stucked at MAN status.

Transferring data at end of night

• Use a linux window in puma, and go to the directory where you have the data. For example
  cd DATA
• Now you can transfer the data with:
  scp -r SWO_DC_20111124_25 observer@csp2:/raw
  where you have to replace 'observer' by your username in csp2 machine
• Then, the computer will request you your password in csp2 machine. And after that, it will transfer the data.
  You can close the telescope while this command works.

Closing the Telescope

• Turn OFF power of guiding camera in lightblue rack
• Push OBTURADOR on console to close shutter
• Push ASENCION RECTA on console to turn OFF tracking
• In TCC-Guider PC, type 'DOME IDLE' to de-activate dome rotation
• In TCC-Guider PC, type 'DOME PARK' to park dome to the south
• In TCC-Guider PC, type 'COVER' (telescope will slew south)
• Go to the platform, raise platform, and put on the telescope cover
• Lower platform
• Rise windscreen
• Turn OFF fans in adjacent room (turn OFF switch and set reostat to zero)
• In TCC-Guider PC, type 'ZENITH' (telescope will slew to the zenith)
• Turn Power OFF on console
• Turn console OFF (rotate key)
• Turn OFF monitors in control room
• In 'gdr' window click CENTERFIELD
• Fill out Night Report here
• You can go party now

Shutter timing and linearity tests (alternative program for cloudy nights)

If you cannot open the dome because it is overcast, it would useful if you could carry out
shutter timing and linearity tests following the following instructions:


• Shutter test
  • Wait until the sky is dark and close the dome.
  • Turn off the incandescent lights from the console.
  • Point the telescope to the zenith.
  • Set the subraster to [1310:1510,501:701]
  • Turn on the quartz lamp and adjust the intensity until you get about 10 kcounts/pix in 30 sec. Then use the MULTIPLE option to get a 10x3sec exposures, followed by a single 30sec expsoure. Repeat this procedure until
    you have about 10 pairs of long-short images.
    
• Linearity test
  • (Mario Exposure Times)
  • Wait until the sky is dark and close the dome.
  • Turn off the incandescent lights from the console.
  • Point the telescope to the zenith
  • Set the subraster to [1310:1510,501:701]
  • Turn on the quartz lamp and adjust the intensity until you get 100 counts/pixel (above the bias which is ~600 counts/pix) in 8 seconds.
    Then take exposures of 4, 8, 16, 8, 24, 8, 32, 8, 48, 8, 64, 8, 80, 8, 96, 8, 120, 8, 144, 8, 180, 8, 240, 8, 320, 8, 400, 8, 500, 8, 600,
    8, 700, 8, 800, 8, 1000, 8, 1200, 8, 1300, 8, 1400, 8, 1500, 8, 1600, 8, 1700, 8, 1800, 8. Feel free to stop this sequence when
    you reach 24 kcounts/pix. The 8 sec exposures are used to control the illumination variations. With the task imstat you can
    check the illumination level in the 8-sec exposures. If you notice large (> 3%) variations please get another sequence.
  • (Carlos Exposure Times - Optional)
  • Turn on the quartz lamp and adjust the intensity until you get 200 counts/pixel above the bias (which is ~700 counts/pix) in 8 seconds.
    Then take exposures of 8, 8, 8, 12, 8, 16, 8, 20, 8, 28, 8, 24, 8, 28, 8,
    32, 8, 36, 8, 40, 8, 80, 8, 120, 8, 160, 8, 200, 8, 240, 8, 280, 8, 320, 8,
    360, 8, 400, 8, 440, 8, 480, 8, 520, 8, 560, 8, 600, 8, 640, 8, 680,
    8, 720, 8, 760, 8, 800, 8.
    If possible, take another sequence.