[daip] question about FLATN, OHGEO

[Deborah Haarsma]

Dear analysts,

Larry Molnar and I are long time radio astronomers, but we also work with data from Calvin College's small optical telescope.   Amateur astronomy software works well enough for basic optical reduction, but when we need a specialized task we tend to turn to AIPS.   One of our students, Jess Vriesema, has photographed 98 CCD images in the field of Andromeda and we want to combine them into a large mosaic.   He ran the individual images through Pinpoint(tm), an astrometry engine which we have found to work well in other projects.  Then we brought the images into aips to correct the geometric projection over the large field.  The FLATN procedure seems ideal for the task; when we run it, the global geometry seems corrected, but there are double stars on the boundaries between fields.   We then ran OHGEO on the files individually to get a better feel for what's going on, referencing them to the center of Andromeda a few fields away.  I've attached four files - two different fields (S32 and S33), before and after OHGEO.   The two fields have a strip of overlap (S32 is south of S33); the stars in this strip have the same RA and Dec before OHGEO, but rather different RA and Dec afterward.   In the headers of the files after OHGEO, you can see that AIPS has moved the CD and TR keywords into the history.  I expected OHGEO to keep modified versions of these keywords in the header.  Do FLATN and OHGEO read the CD and TR keywords?  Is there some option we're setting incorrectly in order to do the mosaic?  We appreciate your help on this matter.  We can send further data files as you have questions. 

Deb Haarsma, for Jess Vriesema and Larry Molnar




~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Prof. Deborah B. Haarsma
email: dhaarsma at calvin.edu
mail: 1734 Knollcrest Circle SE, Grand Rapids, MI 49546
office: Science Building 175
phone: 616-526-6340  fax: 616-526-6501
web: http://www.calvin.edu/~dhaarsma


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