Change parameter of source extraction

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Jerry Zhang

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Jul 25, 2022, 1:19:23 PMJul 25
to astrometry
Hi, 

Is there any way to change the source extraction parameters? My images sometimes contain over-saturated stars, noises, artifacts, spikes, and I would like to adjust some thresholds to filter some detections, and knowing some extraction outputs like the extraction quality for each source, the backgrounds, is a star or a galaxies etc.... WITHOUT the installation of SEXtractor (I know there is an option to use SEXtractor  but I am struggling in installing it)

Cheers,
Jerry

Dustin Lang

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Jul 25, 2022, 2:05:27 PMJul 25
to Jerry Zhang, astrometry
Hi,

Not really -- the built-in Astrometry.net source extraction is very simple, we don't really measure very much about the sources other than their peak locations and rough brightness.

You could look at using "photutils" if Source Extractor is difficult to install.  I haven't used photutils' source detection routines, but that's not rocket surgery so it's probably okay.  Not sure how much they have by way of masking or measurements.

cheers,
dustin

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Dustin Lang

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Jul 25, 2022, 2:07:14 PMJul 25
to Jerry Zhang, astrometry
Oh, and the simple Astrometry.net source detector can be run separately -- it's the "image2xy" program.

About filtering sources: even if a source is saturated, we do want it in the detected source list, because we assume that the brightest stars in the image can be detected.  The built-in source detector tends to still do okay on mildly saturated stars, especially if you do "--downsample 2".

cheers,
dustin

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