Name

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TIC_ONE

Purpose

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Determine the position of the first tic mark for astronomical images.

Explanation

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For use in labelling images with right ascension
and declination axes. This routine determines the
position in pixels of the first tic.

Calling Sequence

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tic_one, zmin, pixx, incr, min2, tic1, [RA = ]

Inputs

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zmin - astronomical coordinate value at axis zero point (degrees
or hours)
pixx - distance in pixels between tic marks (usually obtained from TICS)
incr - increment in minutes for labels (usually an even number obtained
from the procedure TICS)

Outputs

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min2 - astronomical coordinate value at first tic mark
tic1 - position in pixels of first tic mark

Example

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Suppose a declination axis has a value of 30.2345 degrees at its
zero point. A tic mark is desired every 10 arc minutes, which
corresponds to 12.74 pixels. Then
IDL> TIC_ONE, 30.2345, 1, 12.74, min2, tic1
yields values of min2 = 30.333 and tic1 = 5.74, i.e. the first tic
mark should be labeled 30 deg 20 minutes and be placed at pixel value
5.74

Revision History

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by B. Pfarr, 4/15/87
Converted to IDL V5.0 W. Landsman September 1997