Astronomical Applications Department, U.S. Naval Observatory novas c 2 doc Page 18
18
4.5
VIRTUAL_STAR
short int virtual_star (double tjd, body *earth, cat_entry *star,
double *ra, double *dec)
PURPOSE:
Computes the virtual place of a star at date `tjd', given its
mean place, proper motion, parallax, and radial velocity for
J2000.0.
INPUT
ARGUMENTS:
tjd (double)
TT (or TDT) Julian date for virtual place.
*earth (struct body)
Pointer to structure containing the body designation for the
Earth (defined in novas.h).
*star (struct cat_entry)
Pointer to catalog entry structure containing J2000.0 catalog
data with FK5-style units (defined in novas.h).
OUTPUT
ARGUMENTS:
*ra (double)
Virtual right ascension in hours, referred to mean equator
and equinox of J2000.
*dec (double)
Virtual declination in degrees, referred to mean equator
and equinox of J2000.
RETURNED
VALUE:
(short int)
0...Everything OK.
>0...Error code from function `solarsystem'.
Discussion:
See the discussion for function app_star. Function virtual_star is identical to
app_star in input arguments and use. Here, however, the output arguments provide the
virtual place of the star. The virtual place is essentially the apparent place expressed in
the coordinate system of standard epoch J2000.0.
