The Palomar ``green sheet''

 When filling out the observing run ``green sheet'' for a run that uses the Fabry-Perot, there are a number of special requirements that should be noted:

• Request a bottle of dry nitrogen.
  At both the 60- and 200-inch telescopes, a bottle of dry nitrogen is required for keeping the etalon dry and clean. A standard regulator is included with the instrument equipment.

• At the 60-inch telescope, request the ``big shutter''.
  At the 60-inch telescope, the simplest shutter to use is the one built-in to the telescope base. The Palomar crew will probably install this anyway, but it is best to note this on the green sheet, just to be sure.

• At the 200-inch telescope, request the F/9 base, without the shutter.
  The Fabry-Perot is attached to the F/9 guider base on the 200-inch telescope. Although the mountain staff should be aware of the need for this base, it should be specifically mentioned in the green sheet. You will also need to note that the built-in shutter in the F/9 guider base will not be used and should be removed. The Fabry-Perot uses an internal shutter at the 200-inch telescope, due to a clearance problem between the built-in shutter solenoid in the F/9 base and the enlarged 3-inch square filter holders. Once the guider base is installed, it is not a trivial task to remove the shutter. Finally, by noting the F/9 focal ratio, you will also ensure that the F/9 optics are placed into the telescope beam.

• At the 200-inch telescope, request the COSMIC instrument.
  On the 200-inch telescope one has the ability to set-up both a Cassegrain instrument (i.e., the Fabry-Perot) and a prime focus instrument. In the course of observations, the secondary mirror can be moved in a manner of minutes to switch between the Cassegrain and prime foci. It is therefore recommended that you request that the COSMIC instrument (a prime focus imaging spectrograph) be set-up for the run, essentially as a backup instrument, in case of difficulties with the Fabry-Perot.

• Note the need for daytime calibrations.
  Fabry-Perot data sets require large numbers of calibration frames, which are best obtained outside of normal observing hours. You should note on the green sheet that a couple of hours will be needed for calibrations in both the morning and evening. In principle, calibrations can be obtained at the 60-inch telescope at almost any time (except when the dewar is being filled, etc.). The 200-inch telescope, however, is open for public viewing between the hours of 9:00 am and 4:00 pm daily, during which time the lights cannot be extinguished. Although bias frames can still be obtained, flatfield and calibration lamp images should probably be obtained outside of these hours. (Before bed and during dinner are often the most convenient times for calibrations anyway.) The observatory staff should be notified on the green sheet of the need to take daytime calibrations.

• CCD choice.
  The ideal CCD choice for the Fabry-Perot is one of the 24µm-pixel 1024 × 1024 arrays, such as CCD #15 or #16. The beam size of the instrument is well-matched to these arrays, but much too small to make use of the larger 2048 × 2048 detectors (e.g., CCD #13). More importantly, at the 60-inch telescope, the Fabry-Perot instrument is long enough that only certain CCD dewars can be mounted and still clear the fork of the telescope. CCD #15 is the only choice at the 60-inch telescope, for this reason. Although the dewar on CCD #16 will not pass through the fork on the 60-inch telescope, it is often the detector of choice at the 200-inch telescope. CCD #16 is slightly better than CCD #15 in a cosmetic sense, as well as being slightly thinner, and therefore less sensitive to cosmic rays. A third option at the 200-inch telescope is to use one of the large arrays (e.g., CCD #13), but only save the relevant portion of the chip. This allows the user to take advantage of a chip with higher quantum efficiency, at the expense of a longer read-out time. Check the Palomar web pages for specific characteristics of the available CCDs. The recommended detectors are summarized in Table 1.
     

  Table 1: Available CCD cameras for use with the Fabry-Perot system.

  detector	dimensions [pixels]	pixel size [µm]	gain [e-/ADU]	read noise [e-]	telescope
  CCD #15	1024 × 1024	24	2.0	6.6	P60/P200
  CCD #16	1024 × 1024	24	2.5	8.2	P200
  CCD #13	2048 × 2048	24	1.6	6.3	P200