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bad coadd.fits from SDSS mosaic
12-30-2011, 19:17 (This post was last modified: 12-31-2011 17:43 by CT Smith.)
Post: #1
bad coadd.fits from SDSS mosaic
Hi all,
I'm a bit of a newbie so I'm sorry if this is just because of something I missed. I'm trying to resample and combine sets of SDSS images which fall with in a particular radius of a source. As a result I'm working with images from different runs and taken with different ccds. I'm using 2.19.1 compiled (from source code) on Ubuntu Oneiric 11.10 and can't seem to get things working properly. (I haven't quite figured out how to get the RPM installed, sadly enough).

Initially I tried to resample and combine the images (I'm working with 5 or so) in one run, but no mater how I fiddled with the configuration file I could only get at best a final coadd.fits with all zeros (once I managed to get a single pixel with a 10^6 value, but that was a bit of a fluke). I then tried to just combine them without resampling and managed to get a somewhat mutilated version of the mosaic I was looking for (see attached image, should be only one galaxy). I thought that it might have something to do with this particular set of images, but I got the same result with an entirely different set as well.

I poked around here and found some interesting leads (like this one re: combining images with different CTYPEs
) but I haven't been able to turn up anything that works. I'd really appreciate any help with this, and again I'm sorry if this is mostly stupidity on my part.
Thanks,
CT


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01-05-2012, 18:54
Post: #2
RE: bad coadd.fits from SDSS mosaic
Hi CT,

weird. I use SWarp frequently with SDSS images myself, and I have never seen that. Could you check with (unstable) version 2.6.30 on the SVN repository and tell me if it behaves better? Thanks!
- Emmanuel.
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01-06-2012, 22:48
Post: #3
RE: bad coadd.fits from SDSS mosaic
Hi Emmanuel,

Thanks for the reply! I tried the other version and it gave me the same thing (exactly the same, actually).

CT

(01-05-2012 18:54)Emmanuel Bertin Wrote:  Hi CT,

weird. I use SWarp frequently with SDSS images myself, and I have never seen that. Could you check with (unstable) version 2.6.30 on the SVN repository and tell me if it behaves better? Thanks!
- Emmanuel.
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01-08-2012, 22:22
Post: #4
RE: bad coadd.fits from SDSS mosaic
Well well. Would you mind sending me a small archive with an example of data that causes trouble (+your preferred configuration file and execution line)?
Thank you!
- Emmanuel.
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01-27-2012, 21:16
Post: #5
RE: bad coadd.fits from SDSS mosaic
OK, looking at your data, I see that each of the FITS files has an extra extension that contains a 2048x1 "image" (1D flatfield?). This confuses SWarp because it is expressed in a completely different coordinate system. So you must tell SWarp to restrict the processing to the main HDU ("extension" #0) by adding a "[0]" to each filename, as in image.fits[0].
Best,
- Emmanuel.
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01-29-2012, 03:03
Post: #6
RE: bad coadd.fits from SDSS mosaic
Thank you so much! That fixed the problem!
-CT
(01-27-2012 21:16)Emmanuel Bertin Wrote:  OK, looking at your data, I see that each of the FITS files has an extra extension that contains a 2048x1 "image" (1D flatfield?). This confuses SWarp because it is expressed in a completely different coordinate system. So you must tell SWarp to restrict the processing to the main HDU ("extension" #0) by adding a "[0]" to each filename, as in image.fits[0].
Best,
- Emmanuel.
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