This function converts star positions from the IAU 1976, FK5, Fricke system to the Bessel-Newcomb, FK4 system.

palFk54z( double r2000, double d2000, double bepoch, double $\ast$r1950, double $\ast$d1950, double $\ast$dr1950, double $\ast$dd1950 )

r2000 = double (Given)

d2000 = double (Given)

bepoch = double (Given)

r1950 = double $\ast$ (Returned)

d1950 = double $\ast$ (Returned)

dr1950 = double $\ast$ (Returned)

dr1950 = double $\ast$ (Returned)

• The proper motion in RA is dRA/dt rather than cos(Dec)$\ast$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.