Welcome to the L3 Harris Geospatial documentation center. Here you will find reference guides and help documents.
﻿
>  Docs Center  >  Libraries  >  ASTROLIB  >  ALTAZ2HADEC

ALTAZ2HADEC

ALTAZ2HADEC

Purpose

Convert Horizon (Alt-Az) coordinates to Hour Angle and Declination.

Explanation

Can deal with the NCP singularity. Intended mainly to be used by
program hor2eq.pro

Calling Sequence

ALTAZ2HADEC, alt, az, lat, ha, dec

Inputs

alt - the local apparent altitude, in DEGREES, scalar or vector
az - the local apparent azimuth, in DEGREES, scalar or vector,
measured EAST of NORTH!!! If you have measured azimuth west-of-south
(like the book MEEUS does), convert it to east of north via:
az = (az + 180) mod 360
lat - the local geodetic latitude, in DEGREES, scalar or vector.

Outputs

ha - the local apparent hour angle, in DEGREES. The hour angle is the
time that right ascension of 0 hours crosses the local meridian.
It is unambiguously defined.
dec - the local apparent declination, in DEGREES.

Example

Arcturus is observed at an apparent altitude of 59d,05m,10s and an
azimuth (measured east of north) of 133d,18m,29s while at the
latitude of +43.07833 degrees.
What are the local hour angle and declination of this object?
IDL> altaz2hadec, ten(59,05,10), ten(133,18,29), 43.07833, ha, dec
===> Hour angle ha = 336.683 degrees
Declination, dec = 19.1824 degrees
The widely available XEPHEM code gets:
Hour Angle = 336.683
Declination = 19.1824

Revision History

Written Chris O'Dell Univ. of Wisconsin-Madison May 2002

© 2020 Harris Geospatial Solutions, Inc. |  Legal
My Account    |    Store    |    Contact Us