mscimatch - not accepting solution

mmcd wrote on Jul 08, 2008

Hi all,

I'm running mscimatch on a pair of images, and although I have "accept=yes", the scaling isn't applied to the images. Is this the way it is supposed to be? I'd like this step to be automated if possible...

My exact syntax is:
mscimatch refim,othim stars.wcs accept=yes scale+ zero- box1=11 box2=15 lower=-50 niterate=2 sigma=3 interactive- verbose+

And the output is:
MSCIMATCH:
Reading region coordinates from stars.wcs
1682 coordinates read
Measuring regions in refim ...
1081 good regions measured
Measuring regions in othim ...
1077 good regions measured
Determining scale factors ...
refim: 1.0000 (0.0000) 0.00 (0.00)
othim: 0.5641 (0.0093) 0.00 (0.00)

Thanks,
-Mike

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Mike Fitzpatrick wrote on Jul 08, 2008

Try unlearning the task, or else make sure the 'update' parameter is enabled. The way the task is written, the header is only updated if the parameter is set, and the 'accept' param is only used when in interactive mode (otherwise the update is automatic anyway).

Cheers,
-Mike

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Francisco Valdes wrote on Jul 08, 2008

Hello Mike,

MSCIMATCH only computes scale factors; it does not actually scale the pixel values. The concept is that you use this task to compute scale factors based on rough photometry and then you either use the logged factors or the keywords added to the headers. The recommended procedure is that after MSCIMATCH adds the keywords you then run MSCSTACK, which is really just IMCOMBINE, where the scaling parameters are set to point to the header keywords. The images are then scaled "on-the-fly" for stacking. You could manually scale the images with something like IMARITH or IMEXPR and then combine without any scaling. But generally you only need to scale the data when combining.

You might want to look at

http://www.noao.edu/noao/noaodeep/ReductionOpt/frames.html

for some real usage discussion. In particular section III.G

Yours,
Frank Valdes

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Last post on Jul 08, 2008