Assembling the input catalogues

You need to prepare two catalogues: one containing the observations of the standard stars, the other the observations of the programme objects. Neither catalogue is likely to contain more than, at most, a few score entries. The most convenient way to create these catalogues is to use the STL format (see Appendices  and ) and type them in using an editor. Note that separate sets of catalogues should usually be prepared for each night that observations were made; observations from different nights should not normally be combined prior to calibration.

The instrumental magnitudes will be assembled from the output of other programs, such as PHOTOM. The standard or catalogue magnitudes will ultimately come from the catalogues of standards which you used when selecting the standard stars to observe. The air mass (or zenith distance) will often be included in either your observing logs or the header information of your CCD frames. If the air mass is not available then the CURSA applications can automatically calculate it from the zenith distance. Note that it is the observed zenith distance, that is as affected by atmospheric refraction, which is required. If the zenith distance is not available either then you will have to calculate it from whatever information you have about the celestial coordinates and times of your observations. Most standard textbooks on spherical astronomy give the requisite formulæ (see, for example, Spherical Astronomy by R.M. Green[15]).

The catalogues of standard stars and programme objects are discussed separately below.