Name

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      TICS

Purpose

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      Compute a nice increment between tic marks for astronomical images.

Explanation

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      For use in labelling a displayed image with right ascension
      or declination axes. An approximate distance between tic
      marks is input, and a new value is computed such that the
      distance between tic marks is in simple increments of the
      tic label values.

Calling Sequence

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      tics, radec_min, radec_max, numx, ticsize, incr, [ /RA ]

Inputs

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      radec_min - minimum axis value (degrees)
      radec_max - maximum axis value (degrees)
      numx - number of pixels in x direction

Input/output

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      ticsize - distance between tic marks (pixels)

Outputs

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      incr - incremental value for tic labels (in minutes of
              time for R.A., minutes of arc for dec.)

Revison History

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      written by B. Pfarr, 4/14/87
      Added some more tick precision (i.e. 1 & 2 seconds in case:) EWD May92
      Added sub arcsecond tick precision W. Landsman May 2000
      Plate scale off by 1 pixel W. Landsman July 2004