palPreces
palPreces
- Precession - either FK4 or FK5 as required
- Description:
- Precess coordinates using the appropriate system and epochs.
- Invocation:
- void palPreces ( const char sys[3], double ep0, double ep1,
double
ra, double
dc );
- Arguments:
-
-
sys = const char [3] (Given)
-
Precession to be applied: FK4 or FK5. Case insensitive.
-
ep0 = double (Given)
-
Starting epoch.
-
ep1 = double (Given)
-
Ending epoch
-
ra = double
(Given & Returned)
-
On input the RA mean equator & equinox at epoch ep0. On exit
the RA mean equator & equinox of epoch ep1.
-
dec = double
(Given & Returned)
-
On input the dec mean equator & equinox at epoch ep0. On exit
the dec mean equator & equinox of epoch ep1.
- Notes:
- Uses palPrec for FK5 data and palPrebn for FK4 data.
- The epochs are Besselian if SYSTEM='FK4' and Julian if 'FK5'.
For example, to precess coordinates in the old system from
equinox 1900.0 to 1950.0 the call would be:
palPreces( "FK4", 1900.0, 1950.0, &ra, &dc );
- This routine will NOT correctly convert between the old and
the new systems - for example conversion from B1950 to J2000.
For these purposes see palFk425, palFk524, palFk45z and
palFk54z.
- If an invalid SYSTEM is supplied, values of -99D0,-99D0 will
be returned for both RA and DC.