### SLA_PM

Proper Motion

ACTION:
Apply corrections for proper motion to a star $\left[\phantom{\rule{0.3em}{0ex}}\alpha ,\delta \phantom{\rule{0.3em}{0ex}}\right]$.
CALL:
CALL sla_PM (R0, D0, PR, PD, PX, RV, EP0, EP1, R1, D1)
##### GIVEN:
 R0,D0 D $\left[\phantom{\rule{0.3em}{0ex}}\alpha ,\delta \phantom{\rule{0.3em}{0ex}}\right]$ at epoch EP0 (radians) PR,PD D proper motions: rate of change of $\left[\phantom{\rule{0.3em}{0ex}}\alpha ,\delta \phantom{\rule{0.3em}{0ex}}\right]$ (radians per year) PX D parallax (arcsec) RV D radial velocity (km s${}^{-1}$, +ve if receding) EP0 D start epoch in years (e.g. Julian epoch) EP1 D end epoch in years (same system as EP0)

##### RETURNED:
 R1,D1 D $\left[\phantom{\rule{0.3em}{0ex}}\alpha ,\delta \phantom{\rule{0.3em}{0ex}}\right]$ at epoch EP1 (radians)

NOTES:
(1)
The $\alpha$ proper motions are $\stackrel{̇}{\alpha }$ rather than $\stackrel{̇}{\alpha }cos\delta$, and are in the same coordinate system as R0,D0.
(2)
If the available proper motions are pre-FK5 they will be per tropical year rather than per Julian year, and so the epochs must both be Besselian rather than Julian. In such cases, a scaling factor of 365.2422D0/365.25D0 should be applied to the radial velocity before use also.
REFERENCES:
(1)
1984 Astronomical Almanac, pp B39-B41.
(2)
Lederle & Schwan, 1984. Astr. Astrophys. 134, 1-6.