Astronomical Applications Department, U.S. Naval Observatory novas c 2 doc Page 28
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These two transformations correspond to
option
= 1 and
option
= 2, respectively.
Option
= 3 requests both transformations, and is the most common case.
This function should be used only for stars with linear space motion; do not use for
components of orbit binaries. Also, this function cannot be properly used to bring data
from old (pre-FK5) star catalogs into the modern system, because old catalogs were
compiled using a set of constants that are incompatible with the IAU (1976) system.
