This is to announce the start of the 30-day Public Comment Period on
2 FITS conventions that deal with geometric distortions in images. The
first convention, called Simple Imaging Polynomial or SIP, represents
non-linear geometric distortion of the coordinate system via polynomial
coefficients in FITS header keywords.

The second convention, called TNX, extends the standard tangent plane
WCS convention by adding a non-linear distortion function defined by
polynomial coefficients that are stored using indexed WATj_nnn keywords.

Detailed information about these conventions is available for public
review and comment from the FITS registry web page at

http://fits.gsfc.nasa.gov/fits_registry.html

Comments may be posted here on the FITSBITS mail exploder or the
sci.astro.fits newsgroup. Minor typographical issues may be sent
directly to the authors of the convention.

Bill Pence
(on behalf of the IAU FITS Working Group)
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__________________________________________________ __________________
Dr. William Pence
NASA/GSFC Code 662 HEASARC +1-301-286-4599 (voice)
Greenbelt MD 20771 +1-301-286-1684 (fax)