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SWarp- combining using sigma clipped average
05-19-2015, 00:12
Post: #1
SWarp- combining using sigma clipped average
Hello,

I am trying to combine some images using sex, scamp and swarp. I want to combine by sigma clipped averaging.

To test if I got sigma clipping working ok: I tried to use swarp to coadd {20 copies of one exposure and one copy of the same exposure but all pixel values multiplied by 3} together. However, the final coadd.fits image didn't clip out the different exposure as an outlier. I also asked swarp to write out a clipped.log, but that log is empty.

Settings:
CLIP_SIGMA 1.0
FSCALE_KEYWORD SWARPSCL (for all 21 inputs, this keyword value was the same)
CLIP_WRITELOG Y
COMBINE_TYPE CLIPPED

Any help in using the sigma clipping function would be much appreciated! I am using the macports SWarp version 2.38.0 (2014-05-22).
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05-28-2020, 10:00
Post: #2
RE: SWarp- combining using sigma clipped average
I had the same issue, and setting the gain to an actual value (instead of GAIN_DEFAULT 0.0) solved it.

I haven't checked this in the source, but it seems plausible that an infinite gain (i.e., what you get by setting it to 0) could prevent pixels from being clipped.

Cheers,
Malte
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