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      Return RA and Dec as character string(s) in sexagesimal format.


      RA and Dec may be entered as either a 2 element vector or as
      two separate vectors (or scalars). One can also specify the precision
      of the declination in digits after the decimal point.

Calling Sequence

      result = ADSTRING( ra_dec, precision, /TRUNCATE )
      result = ADSTRING( ra,dec,[ precision, /TRUNCATE ] )
      result = ADSTRING( dec, [ PRECISION= ]


      RA_DEC - 2 element vector giving the Right Ascension and declination
              in decimal degrees.
      RA - Right ascension in decimal degrees, numeric scalar or vector
      DEC - Declination in decimal degrees, numeric scalar or vector

Optional Input

      PRECISION - Integer scalar (0-4) giving the number of digits after the
              decimal of DEClination. The RA is automatically 1 digit more.
              This parameter may either be the third parameter after RA,DEC
              or the second parameter after [RA,DEC]. If only DEC is supplied
              then precision must be supplied as a keyword parameter. If no
              PRECISION parameter or keyword is passed, a precision of 1 for
              both RA and DEC is returned to maintain compatibility with past
              ADSTRING versions. Values of precision larger than 4 will
              be truncated to 4. If PRECISION is 3 or 4, then RA and Dec
              should be input as double precision.

Optional Input Keyword

      /TRUNCATE - if set, then the last displayed digit in the output is
              truncated in precision rather than rounded. This option is
              useful if ADSTRING() is used to form an official IAU name
              (see http://vizier.u-strasbg.fr/Dic/iau-spec.htx) with
              coordinate specification. The IAU name will typically be
              be created by applying STRCOMPRESS/REMOVE) after the ADSTRING()
              call, e.g.
              strcompress( adstring(ra,dec,0,/truncate), /remove) ;IAU format
        PRECISION = Alternate method of supplying the precision parameter,


      RESULT - Character string(s) containing HR,MIN,SEC,DEC,MIN,SEC formatted
              as ( 2I3,F5.(p+1),2I3,F4.p ) where p is the PRECISION
              parameter. If only a single scalar is supplied it is
              converted to a sexagesimal string (2I3,F5.1).


      (1) Display CRVAL coordinates in a FITS header, H
      IDL> crval = sxpar(h,'CRVAL*') ;Extract 2 element CRVAL vector (degs)
      IDL> print, adstring(crval) ;Print CRVAL vector sexagesimal format
      (2) print,adstring(30.42,-1.23,1) ==> ' 02 01 40.80 -01 13 48.0'
            print,adstring(30.42,+0.23) ==> ' 02 01 40.8 +00 13 48.0'
            print,adstring(+0.23) ==> '+00 13 48.0'
      (3) The first two calls in (2) can be combined in a single call using
          vector input
              print,adstring([30.42,30.42],[-1.23,0.23], 1)

Procedures Called

      RADEC, SIXTY()

Revision History

      Written W. Landsman June 1988
      Addition of variable precision and DEC seconds precision fix.
      ver. Aug. 1990 [E. Deutsch]
      Output formatting spiffed up October 1991 [W. Landsman]
      Remove ZPARCHECK call, accept 1 element vector April 1992 [W. Landsman]
      Call ROUND() instead of NINT() February 1996 [W. Landsman]
      Check roundoff past 60s October 1997 [W. Landsman]
      Work for Precision =4 November 1997 [W. Landsman]
      Major rewrite to allow vector inputs W. Landsman February 2000
      Fix possible error in seconds display when Precision=0
                              P. Broos/W. Landsman April 2002
      Added /TRUNCATE keyword, put leading zeros in seconds display
                              P. Broos/W. Landsman September 2002
      Fix declination zero values under vector processing W.Landsman Feb 2004
      Fix possible problem in leading zero display W. Landsman June 2004
      Assume since V5.4, omit fstring() call W. Landsman April 2006
      Fix significant bug when round a declination with -1<dec<0
          Add PRECISION keyword W.L. Aug 2008
      Use formatting for "+" and "0" W. L. May 2009

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