MSCMATCH FITS header output
Guest wrote on Jul 02, 2006
Hiya,
We need to re-examine in detail a previous astrometric
solution derived using mscmatch on 4m-MOSAIC images.
We have no detailed record of the fit solution
or number of stars used, but
the FITS header in the final merged image is
MSCCMATC= 'Jul 19 0:27 -5.54/1.06 1.000/0.999 0.215/0.238'
I can't find what these numbers mean by Googling around
iraf pages. Could somebody help?
many thanks
Paul
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We need to re-examine in detail a previous astrometric
solution derived using mscmatch on 4m-MOSAIC images.
We have no detailed record of the fit solution
or number of stars used, but
the FITS header in the final merged image is
MSCCMATC= 'Jul 19 0:27 -5.54/1.06 1.000/0.999 0.215/0.238'
I can't find what these numbers mean by Googling around
iraf pages. Could somebody help?
many thanks
Paul
Post generated using Mail2Forum (http://www.mail2forum.com)
Mike Fitzpatrick wrote on Jul 02, 2006
From the source code, the values after the date appear to be the x/y shift of tanget point in arcsec, fractional scale change, and axis rotation in degrees. Additional values after those are the rms in arcsec. Frank may comment in more detail later on.
Cheers,
-Mike
Cheers,
-Mike
Francisco Valdes wrote on Jul 02, 2006
First my apologies for the lack of documentation.
Mike is correct about the values. My only additional comment, which you may already understand, is that MSCCMATCH only applies a global linear correction to the existing geometry information derived from an astrometric field previously. This existing information includes distortions and the detailed placement and orientations of the CCDs. It is assumed that this has not changed from the calibration to your observations. The global linear accounts for the telescope pointing, rotations when mounting the camera, and the effects of refraction.
Yours,
Frank
Mike is correct about the values. My only additional comment, which you may already understand, is that MSCCMATCH only applies a global linear correction to the existing geometry information derived from an astrometric field previously. This existing information includes distortions and the detailed placement and orientations of the CCDs. It is assumed that this has not changed from the calibration to your observations. The global linear accounts for the telescope pointing, rotations when mounting the camera, and the effects of refraction.
Yours,
Frank
Last post on Jul 02, 2006