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authorJoe Hunkeler <jhunkeler@gmail.com>2015-08-11 16:51:37 -0400
committerJoe Hunkeler <jhunkeler@gmail.com>2015-08-11 16:51:37 -0400
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+.help skysep Feb06 noao.nproto
+.ih
+NAME
+skysep -- Compute arc separation of two RA/Dec values
+.ih
+SYNOPSIS
+Given two RA/Dec value pairs the spherical separation is computed. This
+task can be used in scripts and has both text and parameter output.
+.ih
+USAGE
+skysep ra1 dec1 ra2 dec2
+.ih
+PARAMETERS
+.ls ra1, dec1, ra2, dec2
+The RA and Dec of two points on the sky for which a separation is to be
+computed. The RA may be in hours or degrees and the Dec is in degrees.
+The values may be in decimal or sexagesimal format.
+.le
+.ls raunit = "hr"
+Units for right ascension. The value "hr" selects hours and "deg"
+selects degrees.
+.le
+.ls verbose = no
+Print a verbose output to the standard output?
+.le
+.ls sep
+This output parameter will contain the separation in arc seconds after
+the task is run. It may then be referenced as the variable skysep.sep.
+.le
+.ih
+DESCRIPTION
+This simple script task computes the separation between two celestial
+coordinates given as RA and Dec. The RA units may be hours or degrees,
+as selected by a parameter, and the Dec units must be degrees. The result
+may be printed to the standard output (in restricted precision) and is
+also record in a task parameter for later use.
+.ih
+EXAMPLES
+1. The verbose output appears as follows:
+
+.nf
+ cl> skysep 12:12:12 32:32:32 12:12:24 32:32:52 verb+
+ 153.05 arcsec = (12:12:12.00, 32:32:32.0) - (12:12:24.00, 32:32:52.0)
+ cl> = skysep.sep
+ 153.04686934468
+.fi
+
+2. To use in a script:
+
+.nf
+ cache skysep # Cache to avoid problems with updating par files
+
+ # To use scan to get the value.
+ skysep (r1, d1, r2, d2, raunit="deg", verbose+) | scan (sep)
+ printf ("The separation is %f\n", sep)
+
+ # To use the saved value.
+ skysep (r1, d1, r2, d2, raunit="deg", verbose-)
+ printf ("The separation is %.5f\n", skysep.sep)
+.fi
+.ih
+SEE ALSO
+astcalc, asthedit
+.endhelp