%N parang %F $MIR/src/subs/ephem.for
%D Calculate parallactic angle.
%P rjs
%: utilities
%B
        subroutine parang(obsra,obsdec,lst,latitude,chi)

        implicit none
        double precision obsra,obsdec,lst,latitude
        real chi

  This computes the parallactic angle of an alt-az telescope. Accuracy
  is about 0.0003 radians.

  Input:
    obsra )    Apparent RA and DEC of the source of interest (radians).
    obsdec)
    lst        Local sidereal time (radians).
    latitude   Observatory geodetic latitude (radians).

  Output:
    chi        Parallactic angle (radians).
