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    * Converting relative coordinates to absolute:

    Say one wants to convert the RADIO-projected coordinates (+100,+200) arc
    seconds  from  Eq.2000  center  (01:23:45.67,76:54:32.10)  to   absolute
    Eq.2000 coordinates:

      ! Define input offsets
      define double myx myy
      let myx +100
      let myy +200
      ! Define output system of coordinates
      set system eq 2000
      ! Define output projection. NONE means CONVERT output will be absolute
      ! spherical coordinates
      projection /type none
      ! Convert offsets given their input description
      convert 01:23:45.67 76:54:32.10 /type radio /syste eq 2000 /var myx myy /u
      ! Variables are now absolute spherical coordinates
      exa myx myy
      ! Convert to RA-DEC sexagesimal strings
      define char*23 chra chdec
      let chra  myx /sexa h r
      let chdec myy /sexa d r
      exa chra chdec

Gildas manager 2020-09-28