### SLA_H2FK5

Hipparcos to FK5

ACTION:
Transform a Hipparcos star position and proper motion into the FK5 (J2000) frame.
CALL:
CALL sla_H2FK5 (RH, DH, DRH, DDH, R5, D5, DR5, DD5)
##### GIVEN:
 RH D Hipparcos $\alpha$ (radians) DH D Hipparcos $\delta$ (radians) DRH D Hipparcos proper motion in $\alpha$ (radians per Julian year) DDH D Hipparcos proper motion in $\delta$ (radians per Julian year)

##### RETURNED:
 R5 D J2000.0 FK5 $\alpha$ (radians) D5 D J2000.0 FK5 $\delta$ (radians) DR5 D J2000.0 FK5 proper motion in $\alpha$ (radians per Julian year) DD5 D FK5 J2000.0 proper motion in $\delta$ (radians per Julian year)

NOTES:
(1)
The $\alpha$ proper motions are $\stackrel{̇}{\alpha }$ rather than $\stackrel{̇}{\alpha }cos\delta$, and are per year rather than per century.
(2)
The FK5 to Hipparcos transformation consists of a pure rotation and spin; zonal errors in the FK5 catalogue are not taken into account.
(3)
The adopted epoch J2000.0 FK5 to Hipparcos orientation and spin values are as follows (see reference):

 orientation spin $x$ $-19.9$ $-0.30$ $y$ $-9.1$ $+0.60$ $z$ $+22.9$ $+0.70$ mas mas/y

These orientation and spin components are interpreted as axial vectors. An axial vector points at the pole of the rotation and its length is the amount of rotation in radians.

(4)