Standard-star files

Some standard-star files are supplied for the UBVRI and uvby-H-Beta systems. These should be installed in the $MIDASHOME/$MIDVERS/calib/data/pepsys directory; see section if they are not. The files are named UBVSTD.tbl, UVBYST.tbl, saaoUBVRI.tbl, and saaouvbyHB.tbl. The latter two are the E- and F-region standards, established by A.W.J.Cousins.

You can also make new tables of standard stars. The easiest way to make standard-star tables is to begin as though they were program-star tables, but to include columns of standard values in the ASCII file, and field descriptions for them in the format file, before running MAKE/STARTABLE. The standard column names are tabulated in the ``Standard values'' subsection of ``Star tables'' in the Appendix. Don't forget to add the SYSTEM descriptor when you are done!

In making new tables of standard stars, remember that they will be used as extinction stars by the planning program. Therefore, you should look for standards that pass within about 20 degrees of your zenith; this picks a zone of declination centered on your latitude. In right ascension, you want a fairly uniform distribution, so that a standard will be available at large air mass frequently during the night.

The planning program will not select standards that are so near the Sun's right ascension that they can only be observed at large air masses. The instrumental magnitudes of stars that cannot be observed at small air masses must be determined by transforming the standard values to the instrumental system, and these transformed values have relatively large errors; therefore, they contribute relatively little extinction information (see pp. 162-163 of Young [10] for a discussion of this problem, and Beckert and Newberry[1] for examples of transformation errors).

If you must go far from the zenith to pick up standards of rare types, put them in a special file, and treat them as program stars when running the planning program. Then observe them only near the meridian, and don't try to use them as extinction stars. They can still be treated as standards when you run the reduction program.