Hints for the observations


Here a few hints for the observations. In general, one does not have a night assistant. The "only" support which is provided is the refill of the CCD. In case you have troubles or problems you can always call a technician (phone number normally provided at the board in the control room of the 84cm). General information about the observatory, its telescopes and instruments can be found here . Here is the users manual for the 84cm telescope and for Polima . A few more useful items: an Open Office based obslog (prepared by Ivan & Michael) which you can use to either make your obslog during the observations electronically (and mail it to me) or print it out and fill in manually, a table with airmass as function of Dec and HA, and XEphem-catalogs for Prio 1 and Prio 2 sources including Poli-Standards (thx Ivan).

Some hints:

  • To display the images on the DS9 screen properly, flip the images in x and y.
  • Use the Marconi-CCD always with binning = 2. Write careful observing logs and note also the observng conditions (photometric, cloudy etc.). Pls. scan the obslogs after the run (if you use the printouts available at the telescope) or use the new Open Office based obslogs available here and mail them to me.
  • Do a set of 5 biases each at the beginning and end of the night.
  • Do always twilight flats in all four PA in the evening and morning. Best PA-order is PA = 0, 45, 135, 90 in the evening and PA = 90, 45, 0, 135 in the morning. At last three flatfields per PA and session. In general, the exposure level should be between 5000 and 50000 ADU, ideally around 30000 ADU. In case you do not want to take your flats manually, there is the script polima_flat.macros available. It can be loaded within the Polima-GUI (load_macro) and is in the folder "observa". The macro takes automatically 5 flats in each PA with an level of about 30000ADU and does the scaling automatically. Flatfield time starts about 10-15min after sunset and about half an hour before sunrise.
  • Check the pointing of the telescope at the beginning of the night and correct the the coordinates at the telescope. You can either use the eypiece (the small black finder at the telescope) or the finder camera in the control room (the screen to the right of the guiding screen). Don't forget to open the white finder telescope for the latter in the dome. This way you have basically always the object in the field (or at least very close to) of Polima for sources with Dec < 50deg. For higher dec-sources, the telescope has often a large offset of about 10arcmin to the east and about 5arcmin to the north. Here is a list of bright stars close to most sources of our project.
  • For easier observing, we have prepared a catalog, which you can use directly to control the telescope. It can be loaded in the "Control de Telescopio" panel under "Catalogo" (button "archivos"). The catalog has the name SPM_poli-targ-find-stand.obs and can be found in the folder Catalogs. This catalog contains not only the names and positions of the targets, but also their 5 char code (1st column), recommended exposure times (column NF EXTRA), as well as identification on whether the source is of high priority or low priority (1.0 or 2.0 in column mag, respectively) and further down in the column NF EXTRA whether the source is a high-pol or zeropol. std. There in the column mag the brightnesses of the standard stars are given. In addition, for most of our targets positions of bright stars next to them are given which can be used in case of pointing problems.
  • For sources with integration times less than 10min do always a series of 2 polarization measurements with PA = 0, 45, 90, 135, 135, 90, 45 and 0. For integration times of 10min and above one series with PA = 0, 45, 90, 135 is OK. For your convenience, the scripts polima_objeto.macros (2 polarization measurements, 8 images) and polima_objeto_short.macros (1 polarization measurement, 4 images) which can be loaded within the Polima-GUI (load_macro) are available. They are in the folder "observa".
  • For integration times of up to two minutes, no autoguider is required. For the other sources, suitable guide stars are indicated (if already available) in the finder chart via the target list. If you have to search for a guider star by your own, pls. try to find one in the upper part of the GUI. Guider stars in the lower part of the GUI cause reflexes on the CCD!
  • Very rarely the telescope gets stuck when moving from a high-dec source to a low-dec source. In that case, try first to set the telescope back to zenith. If that fails, turn off the "ventilatores" and the "motores" and turn them on again. After that you should be able to put the telescope back to zenith. Check the pointing first before continuing with the observations.
  • Until we have fully understood the instrumental polarization behaviour of Polima, do one polarized and one unpolarized standard each night. Standards and finders can be found either in the target and standard polarization list section or here .
  • We now have an IRAF-based pipeline for automatic data reduction of POLIMA data available. It is installed at the "gama"-computer. You can find the description of it and the pipeline for download in the "internal section" of our SPM-WEB. Although the pipeline is able to identify the objects by their coordinates, you may not only gain by carefully written observing logs but also by putting the proper 5 char name as filename in the Polima-GUI. The IDs for each source can be found in the target list (label 5 Char) or in the 1st column of the source catalog for the telescope control.