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The essential data needed for program stars are names, positions, and the equinox to which the positions are referred. You may also include proper motions and the epoch of the position; spectral types; rough magnitudes, such as might be obtained from the HD; and comments. The command MAKE/STARTABLE helps you create a table of program stars.
Some telescopes record the position toward which the control system thinks the telescope is pointing as part of the data stream, so it is tempting to extract these data to make a positional catalog for the program stars. In general, this is very unwise. The telescopes usually used for photometry generally have neither accurate nor precise pointing.
The precision (repeatability) of the recorded positions does not indicate
their accuracy --- which could be far worse, if the observer adjusted the
zero-points of the telescope's
coordinates to agree with mean places for some equinox
removed a few years in time from the date of observations.
A 2
altitude error corresponds to an airmass error of 0.002 at 2 airmasses,
more than 0.005 at 3 airmasses, and 0.01 airmass at 4 airmasses.
Thus, such errors can cause appreciable systematic errors in extinction
determination and correction.
Although such recorded positions are available (by means of the
CONVERT/PHOT command) as a last resort, they are not recommended.
Good catalog positions should be used whenever they are available.
Standard-star tables also require columns for the standard values, which are often not known for program stars. Because of this difference in content, you should keep standard and program stars in separate table files. You can have several files of each type. The programs will ask for the standard-star files first, and then the program-star files.
You should also plan to keep extinction stars (and other constant objects, such
as comparison stars in variable-star programs) in a separate file from
variable stars.
The reduction program treats standard, constant, and variable stars
differently, so each group should be kept in one or more separate files
(see subsection 
, ``Reduction procedure'').