palFk54z
palFk54z
- Convert a J2000.0 FK5 star position to B1950.0 FK4 assuming
zero proper motion and parallax
- Description:
- This function converts star positions from the IAU 1976,
FK5, Fricke system to the Bessel-Newcomb, FK4 system.
- Invocation:
- palFk54z( double r2000, double d2000, double bepoch, double
r1950,
double
d1950, double
dr1950, double
dd1950 )
- Arguments:
-
-
r2000 = double (Given)
-
J2000.0 FK5 RA (radians).
-
d2000 = double (Given)
-
J2000.0 FK5 Dec (radians).
-
bepoch = double (Given)
-
Besselian epoch (e.g. 1950.0).
-
r1950 = double
(Returned)
-
B1950 FK4 RA (radians) at epoch "bepoch".
-
d1950 = double
(Returned)
-
B1950 FK4 Dec (radians) at epoch "bepoch".
-
dr1950 = double
(Returned)
-
B1950 FK4 proper motion (RA) (radians/trop.yr)).
-
dr1950 = double
(Returned)
-
B1950 FK4 proper motion (Dec) (radians/trop.yr)).
- Notes:
- The proper motion in RA is dRA/dt rather than cos(Dec)
dRA/dt.
- Conversion from Julian epoch 2000.0 to Besselian epoch 1950.0
only is provided for. Conversions involving other epochs will
require use of the appropriate precession functions before and
after this function is called.
- The FK5 proper motions, the parallax and the radial velocity
are presumed zero.
- It is the intention that FK5 should be a close approximation
to an inertial frame, so that distant objects have zero proper
motion; such objects have (in general) non-zero proper motion
in FK4, and this function returns those fictitious proper
motions.
- The position returned by this function is in the B1950
reference frame but at Besselian epoch BEPOCH. For comparison
with catalogues the "bepoch" argument will frequently be 1950.0.