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HADEC2ALTAZ
Converts Hour Angle and Declination to Horizon (alt-az) coordinates.
Can deal with NCP/SCP singularity. Intended mainly to be used by program EQ2HOR
HADEC2ALTAZ, ha, dec, lat ,alt ,az [ /WS ]
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
alt - the local apparent altitude, in DEGREES. az - the local apparent azimuth, in DEGREES, all results in double precision
/WS - Set this keyword for the output azimuth to be measured West from South. The default is to measure azimuth East from North.
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
Written Chris O'Dell Univ. of Wisconsin-Madison May 2002
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