palDe2h
palDe2h
- Equatorial to horizon coordinates: HA,Dec to Az,E
- Description:
- Convert equatorial to horizon coordinates.
- Invocation:
- palDe2h( double ha, double dec, double phi, double
az, double
el );
- Arguments:
-
-
ha = double
(Given)
-
Hour angle (radians)
-
dec = double
(Given)
-
Declination (radians)
-
phi = double (Given)
-
Observatory latitude (radians)
-
az = double
(Returned)
-
Azimuth (radians)
-
el = double
(Returned)
-
Elevation (radians)
- Notes:
- All the arguments are angles in radians.
- Azimuth is returned in the range 0-2pi; north is zero,
and east is
pi/2. Elevation is returned in the range
/-pi/2.
- The latitude must be geodetic. In critical applications,
corrections for polar motion should be applied.
- In some applications it will be important to specify the
correct type of hour angle and declination in order to
produce the required type of azimuth and elevation. In
particular, it may be important to distinguish between
elevation as affected by refraction, which would
require the "observed" HA,Dec, and the elevation
in vacuo, which would require the "topocentric" HA,Dec.
If the effects of diurnal aberration can be neglected, the
"apparent" HA,Dec may be used instead of the topocentric
HA,Dec.
- No range checking of arguments is carried out.
- 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, and (for tracking a star)
sine and cosine of declination.