Convert horizon to equatorial coordinates.

palDh2e( double az, double el, double phi, double $\ast$ ha, double $\ast$ dec );

az = double (Given)

el = double (Given)

phi = double (Given)

ha = double $\ast$ (Returned)

dec = double $\ast$ (Returned)

• All the arguments are angles in radians.

• The sign convention for azimuth is north zero, east $+$pi/2.

• HA is returned in the range $+$/-pi. Declination is returned in the range $+$/-pi/2.

• The latitude is (in principle) geodetic. In critical applications, corrections for polar motion should be applied.

• In some applications it will be important to specify the correct type of elevation in order to produce the required type of HA,Dec. In particular, it may be important to distinguish between the elevation as affected by refraction, which will yield the " observed" HA,Dec, and the elevation in vacuo, which will yield the " topocentric" HA,Dec. If the effects of diurnal aberration can be neglected, the topocentric HA,Dec may be used as an approximation to the " apparent" HA,Dec.

• No range checking of arguments is done.

• In applications which involve many such calculations, rather than calling the present routine it will be more efficient to use inline code, having previously computed fixed terms such as sine and cosine of latitude.