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astrorama / SourceXtractorPlusPlus

SourceXtractor++, the next generation SExtractor
https://astrorama.github.io/SourceXtractorPlusPlus/
GNU Lesser General Public License v3.0
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is deblending working? #463

Closed plaszczy closed 2 years ago

plaszczy commented 2 years ago

hi, I am new to sourceextractor and fail to get reasonable source positions for some pretty simple image. here are the centroids: src

so obviusly I would like to see 3 objects on the bottom part. The background image is good and here is the segmentation

seg

Looks like no deblending is perfromed on the bottom-pair Also I can't figure out why the segmented image is not binary (but some grey level that has a strong gradient from teh top to bottom of my full image...)

I could not find any information on deblending nor related parameters. Is it implemented?

thanks, cheers stephane

ayllon commented 2 years ago

Hello,

Since 0.16 it should be enabled by default, but older versions have it disabled. Maybe you can check this config file used for the tests to help you set it up?

The segmentation image is not binary because the pixels values corresponds to the detection ids. Sames goes for the partition check image (source ids instead).

Let us know if this helps.

plaszczy commented 2 years ago

thanks. I am using SourceXtractorPlusPlus 0.15 that is the one coming from conda a few days ago. So I will try the config but could you help me indentify which keywords are relevant to deblending? (I suppose "multi-threshold" but what is a partition? is there some doc somewhere?)

btw, this is a nice config file, could be put as the ourtput of -config-file option.

mkuemmel commented 2 years ago

Well, the newest release is 0.16 which is available on conda https://anaconda.org/astrorama/sourcextractor.

--partition-multithreshold switches on deblending; --partition-threshold-count and --partition-minimum-contrast are the parameters to tune the deblending. --partition-minimum-contrast should be set as --detection-minimum-area.

The de-blending works as in Sourcextractor2, you may have a look at the documentation there.

plaszczy commented 2 years ago

OK thanks. where is Sourcextractor2?

mkuemmel commented 2 years ago

In principle its docs are here: https://sextractor.readthedocs.io/en/latest/index.html but it looks like the section on deblending has disappeared. I put the pdf of the docs below. Please check page 22ff. sextractor.pdf

plaszczy commented 2 years ago

hat's cool. thanks very much I now manage to play with deblending. nice work.