stacking dithered mosaic exposures
bomond wrote on Jul 02, 2007
Hi all,
I have a basic WCS on my mosaic images which i'm trying to improve with MSCCMATCH. After that i'm reconstructing the images with MSCIMAGE and stack them with MSCSTACK, following this example: http://www.noao.edu/noao/noaodeep/ReductionOpt/frames.html
But the images just don't match after that. At the centers of the ccds are ok, but closer to the edges of every ccd i see multiple stars. I tryed with higher order of fitting polynomial in MSCCMATCH and with different functions but it doesn't improve very much.
When i plot the catalog positions of the stars over the images with DS9 i see that the WCS is improved after MSCCMATCH, but apparently not enough.
Any ideas what may cause the problem?
cheers,
bomond
I have a basic WCS on my mosaic images which i'm trying to improve with MSCCMATCH. After that i'm reconstructing the images with MSCIMAGE and stack them with MSCSTACK, following this example: http://www.noao.edu/noao/noaodeep/ReductionOpt/frames.html
But the images just don't match after that. At the centers of the ccds are ok, but closer to the edges of every ccd i see multiple stars. I tryed with higher order of fitting polynomial in MSCCMATCH and with different functions but it doesn't improve very much.
When i plot the catalog positions of the stars over the images with DS9 i see that the WCS is improved after MSCCMATCH, but apparently not enough.
Any ideas what may cause the problem?
cheers,
bomond
Francisco Valdes wrote on Jul 02, 2007
Hi,
MSCCMATCH only affects the low order terms of a WCS; namely, the origin, rotation, linear scales, and angle between the axes (skew). To do a full solution you will have to use mscfinder.msctpeak. This is a task based on a package called finder. There is no help page for msctpeak but the interactive help (typing ? when you get the blinking image cursor) is fairly helpful. You might look at
http://iraf.noao.edu/projects/ccdmosaic/astrometry/astrom.html
For some information about WCS.
Yours,
Frank Valdes
MSCCMATCH only affects the low order terms of a WCS; namely, the origin, rotation, linear scales, and angle between the axes (skew). To do a full solution you will have to use mscfinder.msctpeak. This is a task based on a package called finder. There is no help page for msctpeak but the interactive help (typing ? when you get the blinking image cursor) is fairly helpful. You might look at
http://iraf.noao.edu/projects/ccdmosaic/astrometry/astrom.html
For some information about WCS.
Yours,
Frank Valdes
Last post on Jul 02, 2007