C100/WFCCD Observing Procedures

1. Accessing Data Acquisition Computer (clarity)

• Check with the staff for username (either obs100a or obs100b) and password
• Open an xgterm window
• cd /DATA/
• mkdir 20020914_15 (e.g.)
• cd 20020914_15

2. Start Detector Control Window

• In current directory edit file 'filter.names'
  • B
  • V
  • grism_blue
  • I
• In current directory edit file 'aperture.names'
  • Pinhole
  • 150u
  • 750u
  • open
  You can use different names in those files, but if you use the above, the reduction process will be smoother.
• In current directory type 'ccd' to open detector control window
• Before the CCD control window appears you have to select 4 parameters from the menu:
  • WF CCD
  • TEK5
  • 16
  • LCO-100
• On the CCD control window select Gain 1
• On the CCD control window select Subraster and enter the following values:
  • 1 1790 500 1500
  • Apply
  • Done
• Open xgterm window
• Load the 'wfccd' package
• Go to the recently created directory (20020914_15)
• Open XImtool

3. Check Masks and Arc lamps

• Take short (2-sec) exposures of both masks using dome lights. Note than 'Imtype' should be 'object' for all exposures other than bias and dome-flats.
• Make sure image is not saturated and measure slit coordinates with imexam --> (xs,ys) (should be ~1380,500). Zoom in the image in an appropriate way; then place the cursor on the location you will want for your objects at night: choose an ys coordinate (in this example is 500, and it is a good idea to keep it the same for all the objects), then type the j key which will display in the irafterm a cut along one line across the slit and will give you the xs coordinate. Write down this coordinates in order to use them for the first run of cobject.
• Turn ON He and Ne arc lamps and take short (10-15 sec) exposure.
• Check that wavelength range is correct and that lines are in focus (2-3 pixels wide)
• Check that spectral lines are duly aligned with CCD columns (within 1-2 pixels)
• Please keep this first lamp image because it will be used in the reduction process.

4. Dome Flats and Bias

• Turn OFF platform lights
• Turn ON quartz light and adjust voltage to values given below
• In CCD window set Filter, Aperture=open, Loop=7, exposure time, Imtype=flat, and object="Dome Flat"
  • B: 15 sec (voltage=350)
  • V: 15 sec (voltage=300)
  • I: 5 sec (voltage=250)
• In CCD window set Filter=grism_blue, Aperture=150u/750u, Loop=7, exposure time, Imtype=flat, and object="Dome Flat"
  • 1.65" slit (150u): 10 sec (voltage=480)
  • 8.25" slit (750u): 5 sec (voltage=480)
• Start sequence with START botton
• When the sequence of flats is complete turn OFF quartz lamp
• Make sure you have the grism in the filter wheel (no kidding!)
• Set exptime=0, Imtype=zero, Loop=10, and take a sequence of bias frames

5. Telescope Pointing

• Point to a bright star
• Take direct image while rotating the instrument and determine center of rotation (xr,yr)
• Take direct image
• Compute telescope offset to place star at center of rotation which is probably near (910,500). You can decide to trust these coordinates for the rotation center (it is very stable) and just skip this step.
• Ask the NA to update the ZP of the telescope

6. Telescope Focus

• Set Subraster to OFF
• Point to a bright star
• In CCD window set Loop=7, set filter=V, Exptime=10, and use FOCUS (not START) command
• Imexamine the image (the NA has the value for the last time the instrument was used; it shoud be close to that).
• Turn ON Subraster

7. Observing

• Changing the gain during the night is not recommended since it's easy to forget to reset it.
• Set Imtype=object
• Ask NA to point the telescope to object
• Use 'pangle' to determine paralactic angle and ask the NA to set the rotator angle (Cass. Ring. P.A.). Example: if your object is 2hs20m West from Meridian, type 02:20 in the 'ha' field; if it is 2hs20m East, you should type: -02:20 instead.
• Edit parameters for 'toslit', enter rotator angle, coordinates of rotation center (xcen,ycen), (xs,ys)
• Run 'toslit' and ask the NA to offset the telescope (a big offset which should bring the object close to the slit)
• In CCD window set Aperture=Open, Filter=V, and take direct image of the field
• Edit parameters for 'cobject', set mark=yes, last coordinates measured for the slit, coordinates of guider box, and the object's CCD frame
• Run 'cobject', mark object (space bar), use the CAMERA offset yielded by 'cobject', and ask the NA to move the guider box accordingly
• In CCD window set Filter=B or I, and take another direct image of the field
• In CCD window set Aperture="150u" and take 5-sec exposure of narrow slit mask, display it using imexam and measure (xs,ys)
• Edit parameters for 'cobject', and enter your new values (xs,ys) normally only xs will change
• Run 'cobject', mark object (space bar), use the CAMERA offset yielded by 'cobject', and ask the NA to move the guider box accordingly
• In CCD window set Filter="grism_blue", Aperture="150u", exposure time, object to "object name", and click START to begin exposure
• Turn ON He and Ne lamps, ask the NA to close dome shutter, and take 10-sec exposure (don't forget to remind the NA to disable guider) (DON'T BOTHER TO TAKE LAMPS FOR FLUX STANDARDS)
• Turn OFF He and Ne lamps, and ask the NA to open dome shutter

mhamuy@lco.cl

nmorrell@lco.cl