.help precess Oct87 noao.astutil
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NAME
precess -- general astronomical coordinate precession
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USAGE
precess files startyear endyear
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PARAMETERS
.ls files
The name of a file (or a file list or template) containing the coordinates
to be precessed.
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.ls startyear
The default equinox of the input coordinates.
.le
.ls endyear
The default target year to which the coordinates will be precessed.
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.ls stdepoch = 0
If nonzero, coordinates will be output precessed to both \fBendyear\fR
and the specified standard epoch.
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DESCRIPTION
Coordinates are read from the input file as RA and DEC pairs,
one pair per input line.  Each coordinate pair may optionally be followed
by the equinox of the input coordinates (if different from the default)
and the epoch of the output coordinates.
Coordinates may be entered in either decimal or sexagesimal notation.
The given coordinates are rotated according to the
precession rates to the requested year and printed on the standard output.
Basic data is taken from the Explanation to the American Ephemeris.
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EXAMPLES
Precess coordinate entered interactively from 1950 to 1990, except where
the dates are specified otherwise on the command line (lines input by the
user are marked:

.nf
	cl> precess STDIN 1950 1990			[input]
	12:30:10.12 10:18:27.5				[input]
	  12:32:11.79   10:05:13.09  1990.0
	12:30 10:18					[input]
	  12:32:01.68   10:04:45.51  1990.0
	12:30 -20 1900					[input]
	  12:34:42.89  -20:29:46.29  1990.0
	12:30 -20 1900 2000				[input]
	  12:35:14.40  -20:33:04.40  2000.0
	(eof=<ctrl/z>)					[input]
.fi

The following is equivalent, except that coordinate input is taken from
the file "coords", rather than from the terminal:

.nf
	cl> precess coords 1950 1990			[input]
	  12:32:11.79   10:05:13.09  1990.0
	  12:32:01.68   10:04:45.51  1990.0
	  12:34:42.89  -20:29:46.29  1990.0
	  12:35:14.40  -20:33:04.40  2000.0
.fi
.endhelp
