UVEX - Observing Manual

v2.0 17.September.2007

Opening up
1. See the WFC observing manual
2. To improve the dome seeing you should open the south doors (if weather conditions permit) and the dome (point away from the sun!) about 1-2 hours before sunset.
3. Make sure the IPHAS/UVEX standard star catalogue is included in the TCS. To include the catalogue give the command
  USER> incl iphas_stds
4. You can use the following coordinates as input to staralt to see which IPHAS/UVEX regions you can observe when during the night. These coordinates refer to the first field in each region. A catalogue with field centres generated by Janet Drew can be found here.
5. Important: Make sure the Autoguider is OFF by typing
  SYS> autotv off
  If the autoguider is running you will get additional noise.
  Important: Make sure the CCD readout mode is set to FAST.
Evening twilight sky flats
Move the telescope to a suitable blank field (type
USER> out term
to see a list).
Order of filters: He1, U, r, g.
Try to get at least 3 flat field exposures (20000-40000 ADU) for each filter.
See the WFC observing manual for the offsetting procedure between successive sky flats, to allow the detection of stars in the flat field.
Pointing & Focussing
1. See the WFC observing manual for the zeroset procedure.
  Note: Occasionally the zeroset can trigger quite far from the nominal position (marked by the arrow stickers on the engineering rack). This will cause the pointing to be way off, as you will then notice in the next step. If this happens, simply repeat the zeroset procedure and start closer to the positions indicated by the arrows.
2. See the WFC observing manual for the pointing test (and calibration, if necessary), but first put the He1 filter in to prevent saturation of the calibration star. Changing filters during the pointing calibration results in funky out-of-focus images on the Autoguider!
  After the pointing checks, switch the Autoguider off again.
3. Use the r filter to focus. See the WFC observing manual for the focusrun commands.
4. Once the correct focus position has been determined (the nominal focus is 43.55) then change the value used by the focus command in the /home/intobs/uvex_survey/filter_wrap.csh script.
5. Remember to also issue the focus command manually, to set the correct value after doing the focusrun.
Standard star observations
Check again that the Autoguider is OFF and that the CCD readout is FAST.
Standard star observations are really only necessary if the night is photometric. But as the pipeline needs the observation of standard stars to figure out if the observing was done in cloudy or dusty conditions, they should be taken every night.
Standard star exposures in the evening are taken in twilight when the sky is getting dark and the telescope has been focused.
Try to take 2-3 standard stars in each filter distributed in airmass.
Note: If you have found suitable exposure times for a certain standard star (for which you get a maximum of about 10,000 counts per pixel in decent seeing conditions), you can add those exposure times to the file /home/intobs/uvex_survey/standard.info to allow automated observations of this star in the future. After editing the standard.info file, you can use the script
SYS> /home/intobs/uvex_survey/stdobs.csh "name_of_standard_star"
to automatically observe this standard star.
Important: Check that the standard stars are not saturated, and if necessary lower the exposure times in the file standard.info
Survey observations
Check again that the Autoguider is OFF and that the CCD readout is FAST.
The fields that should be observed are read from the file fields.todo in the /home/intobs/uvex_survey directory. The already observed fields are listed in the file fields.done in the same directory.
1. Change directory to /home/intobs/uvex_survey
2. Copy the correct fields.todo.???.???? file to fields.todo
  The fields.todo.???.???? files are located in the Fields subdirectory
  Try to observe the oldest (2003) files first for a region to have the longest baseline for proper motion.
3. SYS> /home/intobs/uvex_survey/survey_noguide_err.csh
4. If you want to change the observed sky region, change the fields.todo file while the He1, r or U exposure is being taken or read out.
5. To stop the script (after all 4 exposures of a field have been taken), copy the file empty.dat to fields.todo
Note: One standard star should be taken in all filters every 2 hours during the night (see above for automatic script).
Note: To get a real time display of the frames as they are coming in, use the command iphas_rtd in IRAF on the data reduction computer.
Note:
Try to observe with the following constraints:
- Distance from the moon > 30 degrees (must)
- Airmass < 1.4 (if possible)
Note: To see how many fields are still to be observed in the different todo files you can run the following command:
SYS> /home/intobs/uvex_survey/region_status.perl
Note: Never delete the file fields.done! Make a backup copy of this file in case you accidentally overwrite or delete it.
Standard star observations
Standard star exposures in the morning are taken in twilight when the sky is starting to get bright and the observing of UVEX fields has stopped. Try to take 2-3 standard stars in each filter distributed in airmass.
Bias
While you wait for morning twilight to come this is a good oportunity to take some bias frames. Put the He1 filter in (to prevent light leaking through the shutter) and take a maximum of 5 bias exposures. If you are in danger of losing morning twilight flats then forget about the bias frames - flats are more important.
Morning twilight sky flats
Order of filters: g, r, U, He1
Try to get at least 3 flat field exposures (20000-40000 ADU) for each filter.
See the WFC observing manual for the telescope offsetting procedure.
Closing down
See the WFC observing manual