>  Docs Center  >  Libraries  >  ASTROLIB  >  GLACTC_PM






        Convert between celestial and Galactic (or Supergalactic) proper
        motion (also converts coordinates).


      Program to convert proper motion in equatorial coordinates (ra,dec)
      to proper motion in Galactic coordinates (gl, gb) or Supergalacic
      Coordinates (sgl,sgb) or back to equatorial coordinates (j=2).
      The proper motion unit is arbitrary, but be sure to set /MUSTAR if
      units are the projection of the proper motion on the RA, Dec axis.
      It does precession on the coordinates but does not
      take care of precession of the proper motions which is usually a
      very small effect.

Calling Sequence

      GLACTC_PM, ra, dec, mu_ra,mu_dec,year, gl, gb, mu_gl, mu_gb, j,
                  [ /DEGREE, /FK4, /SuperGalactic, /mustar ]

Input Parameters

      year equinox of ra and dec, scalar (input)
      j direction of conversion (input)
1: ra,dec,mu_ra,mu_dec --> gl,gb,mu_gl,mu_gb
2: gl,gb,mu_gl,mu_gb --> ra,dec,mu_ra,mu_dec
  INPUTS OR OUTPUT PARAMETERS: ( depending on argument J )
      ra Right ascension, hours (or degrees if /DEGREES is set),
                        scalar or vector.
      dec Declination, degrees,scalar or vector
      mu_ra right ascension proper motion any proper motion unit
      mu_dec declination proper motion in any proper motion unit
      gl Galactic longitude, degrees, scalar or vector
      gb Galactic latitude, degrees, scalar or vector
      mu_gl galactic longitude proper motion in any time unit
      mu_gb galactic latitude proper motion in any time unit
      All results forced double precision floating.

Optional Input Keyword Parameters

      /DEGREE - If set, then the RA parameter (both input and output) is
                given in degrees rather than hours.
      /FK4 - If set, then the celestial (RA, Dec) coordinates are assumed
              to be input/output in the FK4 system. By default, coordinates
              are assumed to be in the FK5 system. For B1950 coordinates,
              set the /FK4 keyword *and* set the year to 1950.
      /SuperGalactic - If set, the GLACTC returns SuperGalactic coordinates
              as defined by deVaucouleurs et al. (1976) to account for the
              local supercluster. The North pole in SuperGalactic coordinates
              has Galactic coordinates l = 47.47, b = 6.32, and the origin is
              at Galactic coordinates l = 137.37, b= 0
/mustar - if set then input and output of mu_ra and mu_dec are the
                projections of mu in the ra or dec direction rather than
the d(ra)/dt or d(mu)/dt. So mu_ra becomes mu_ra*cos(dec)
              and mu_gl becomes mu_gl*cos(gb).


      Find the SuperGalactic proper motion of M33 given its
      equatorial proper motion mu* =(-29.3, 45.2) microas/yr.
      Where the (*) indicates ra component is actual mu_ra*cos(dec)
(Position: RA (J2000): 01 33 50.9, Dec (J2000): 30 39 36.8)
      IDL> glactc_pm, ten(1,33,50.9),ten(30,39,36.8),-29.3,45.2, 2000,$
      ==> SGL = 328.46732 deg, SGB = -0.089896901 deg,
mu_sgl = 33.732 muas/yr, mu_gb = 41.996 muas/yr.
        And for the roundtrip:
      IDL> glactc_pm, ra,dec,mu_ra,mu_dec,2000,$
      IDL> sgl,sgb,mu_sgl,mu_sgb,2,/Supergalactic,/mustar
        ==> ra=1.5641376 hrs., dec= 30.660277 deg,
            mu_ra= -29.300000 muas/yr, mu_dec=i 45.200000 muas/yr

Procedure Calls



      Written Ed Shaya, U of MD, Oct 2009.
      Adapted from GLACTC to make proper motion transformations,
      Correct occasional sign error in galactic longitude E. Shaya Nov 2011

© 2022 Harris Geospatial Solutions, Inc. |  Legal
My Account    |    Store    |    Contact Us