search

dstndstn / astrometry.net

Astrometry.net -- automatic recognition of astronomical images
http://astrometry.net
Other
661 stars 185 forks source link

WCS parameters meaning #236

Closed lkosz closed 2 years ago

lkosz commented 2 years ago

Hello

Is there a documentation explaining the meaning of the parameters in wcs files?

dstndstn commented 2 years ago

Hi,

The standards documents are here, https://fits.gsfc.nasa.gov/fits_wcs.html

Short version: we use a TAN WCS projection, ie, a tangent-plane projection. CRPIX tells you where on the image the projection is centered CRVAL tells you the RA,Dec of that point. the CD matrix tells you how pixels project into the directions of RA and Dec; those vectors ("intermediate world coordinates") get projected back onto the sphere to give RA,Dec.

cheers, --dustin

On Fri, Sep 3, 2021 at 8:23 PM lkosz @.***> wrote:

Hello

Is there a documentation explaining the meaning of the parameters in wcs files?

— You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub https://github.com/dstndstn/astrometry.net/issues/236, or unsubscribe https://github.com/notifications/unsubscribe-auth/AAIEH7PMFG6UEF4E6G4MZNDUAFRJRANCNFSM5DMVWGIA . Triage notifications on the go with GitHub Mobile for iOS https://apps.apple.com/app/apple-store/id1477376905?ct=notification-email&mt=8&pt=524675 or Android https://play.google.com/store/apps/details?id=com.github.android&referrer=utm_campaign%3Dnotification-email%26utm_medium%3Demail%26utm_source%3Dgithub.