Astro-FITS-HdrTrans
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=over 4
=item B<to_ROTATION>
This determines the angle, in decimal degrees, of the declination or
latitude axis with respect to the second axis of the data array, measured
in the anticlockwise direction.
It first looks for the linear-transformation CD matrix, widely used
including by IRAF and the precursor to the PC matrix. If this is
absent, the routine attempts to find the standard transformation
matrix PC defined in the FITS WCS Standard. Either matrix is
converted into a single rotation angle.
In the absence of a PC matrix it looks for the CROTA2 keyword from the
AIPS convention.
The evaluation from the CD matrix is based upon Micah Johnson's
cdelrot.pl script supplied for use with XIMAGE, extended to average
the two estimates using FITS-WCS Paper II Section 6.2 prescription.
( run in 0.222 second using v1.01-cache-2.11-cpan-4d50c553e7e )