iraf.net

From: Josh Walawender <walawend@solo.colorado.edu>
Date: May 11, 2005 11:00:37 AM MST
To: Frank Valdes <valdes@noao.edu>
Subject: MSCSETWCS question
Hi Frank, I'm having some trouble applying the new database I created with
msctpeak to some images. This is Mosaic II data from CTIO, taken
shortly after a CCD chip was swapped out in the instrument. I can't
find a new astrometric solution on the website, so I generated a
database with msctpeak and the fit looked excellent with solely random
noise and no systematic shifts visible in the various plots of
residuals. However when I apply that database solution to the same
image I used to create it and then run msccmatch, I get a very clear
systematic error in the residuals. I've checked the database and the
headers based on the problem we were having before and the database has
the "begin im1" lines correct for all 8 extensions and the header has
the "EXTNAME = im1" header info correct for all extensions. I've generated the database twice, the second time I increased
the order of the fit (xx, xy, yx, and yy order increased from 4 to 5),
but the msccmatch fit looks the same. I've attached a file with the headers (hdrs), a file with the
database solution (sa110.db), and a jpeg of the residuals of the
msccmatch fit (msccmatch1.jpg). Any insight you could give me would be
greatly appreciated.thanks,
Josh-------------------------------------------
Josh Walawender (joshw@colorado.edu)
Center for Astrophysics and Space Astronomy
University of Colorado at BoulderOffice: C328
Phone: x2-4053
Campus Box 389 Boulder, CO 80309
http://solo.colorado.edu/~walawend/
-------------------------------------------
From: Frank Valdes <valdes@noao.edu>
Date: May 17, 2005 2:26:18 PM MST
To: Josh Walawender <walawend@solo.colorado.edu>
Subject: Re: MSCSETWCS questionHi Josh,I believe your problem is that you specified "tan" for the projection
type when you used MSCTPEAK. When you apply it to your data it loses
all the higher order distortion terms and what you are seeing from
MSCCMATCH is these distortions. If you edit the database and change
the projection from "tan" to "tnx" then MSCSETWCS will put the higher
order terms into the data.Yours,
Frank