Making an observation

 To assist in the actual observing procedure, a number of scripts have been written; they can be found in the directory sys:[ccd.fp]. The fpseq command in particular can be used to obtain an entire sequence of Fabry-Perot frames at a selection of etalon spacings, including periodic calibration frames for monitoring the stability of the system. See Appendix A below for further information on fpseq and other useful commands.

Once you have properly positioned and oriented the telescope on the target, the observing assistant can help you acquire a guide star. The software interfaces to the guider cameras are currently quite different at the 60-inch and 200-inch telescopes, with the interface for the former being somewhat less automated and therefore more complicated. Regardless, an explanation of the guider interface is beyond the scope of this manual; consult the on-site documentation and the observing assistant to begin guiding on the desired field. Stable guiding is crucial over the course of a Fabry-Perot observation, especially with an etalon such as the Palomar ET-50, which has a large variation in wavelength per pixel.

To start the observation, run fpseq with the desired parameters. You will want to monitor the progress of the observation, particularly at the 60-inch telescope, where user intervention is required to operate the calibration lamp. A sample log sheet is provided in Appendix C, on which you will probably want to record etalon settings, the telescope position and focus, guide star coordinates, weather conditions, etc.