- NAME
HADEC2ALTAZ
- PURPOSE
Converts Hour Angle and Declination to Horizon (alt-az) coordinates.
- EXPLANATION
Can deal with NCP/SCP singularity. Intended mainly to be used by
program EQ2HOR
- ALLING SEQUENCE
HADEC2ALTAZ, ha, dec, lat ,alt ,az [ /WS ]
- NPUTS
ha - the local apparent hour angle, in DEGREES, scalar or vector
dec - the local apparent declination, in DEGREES, scalar or vector
lat - the local latitude, in DEGREES, scalar or vector
- UTPUTS
alt - the local apparent altitude, in DEGREES.
az - the local apparent azimuth, in DEGREES, all results in double
precision
- PTIONAL KEYWORD INPUT
/WS - Set this keyword for the output azimuth to be measured West from
South. The default is to measure azimuth East from North.
- XAMPLE
What were the apparent altitude and azimuth of the sun when it transited
the local meridian at Pine Bluff Observatory (Lat=+43.07833 degrees) on
April 21, 2002? An object transits the local meridian at 0 hour angle.
Assume this will happen at roughly 1 PM local time (18:00 UTC).
IDL> jdcnv, 2002, 4, 21, 18., jd ; get rough Julian date to determine
;Sun ra, dec.
IDL> sunpos, jd, ra, dec
IDL> hadec2altaz, 0., dec, 43.078333, alt, az
===> Altitude alt = 58.90
Azimuth az = 180.0
- EVISION HISTORY
Written Chris O'Dell Univ. of Wisconsin-Madison May 2002