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HADEC2ALTAZ

HADEC2ALTAZ

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

Calling Sequence


      HADEC2ALTAZ, ha, dec, lat ,alt ,az [ /WS ]

Inputs


    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

Outputs


    alt - the local apparent altitude, in DEGREES.
    az - the local apparent azimuth, in DEGREES, all results in double
          precision

Optional 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.

Example


    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

Revision History


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



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