.help skysep Feb06 noao.nproto
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NAME
skysep -- Compute arc separation of two RA/Dec values
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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.
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USAGE	
skysep ra1 dec1 ra2 dec2
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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.
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.ls raunit = "hr"
Units for right ascension.  The value "hr" selects hours and "deg"
selects degrees.
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.ls verbose = no
Print a verbose output to the standard output?
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.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
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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.
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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
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SEE ALSO
astcalc, asthedit
.endhelp
