taskGNU Astronomy Utilities - Tasks: task #16239, NoiseChisel option to avoid...


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task #16239: NoiseChisel option to avoid interpolation for thresholds or Sky

Submitter:  Mohammad Akhlaghi <makhlaghi>
Submitted:  Sat 30 Jul 2022 03:18:35 PM UTC
Should Start On:  Fri 29 Jul 2022 11:00:00 PM UTC Should be Finished on:  Fri 29 Jul 2022 11:00:00 PM UTC
Category:  NoiseChisel Priority:  5 - Normal
Item Group:  Enhancement Status:  Postponed
Privacy:  Public Percent Complete:  0%
Assigned to:  makhlaghi Open/Closed:  Open
Effort:  0.00

Sat 30 Jul 2022 03:18:35 PM UTC, original submission:  

Currently NoiseChisel does nearest neighbor interpolation for estimating the Sky and all the intermediary thresholds (like the quantile threshold and etc). This is done to remove gradients caused by the sky or prior processing steps.

But in some scenarios, the extended signal structure is very large (covering almost all the image) and low-S/N (and therefore not properly detectable). When it is possible to assume that the sky is a constant across the image, in such cases, we can simply use a single constant for our thresholds and Sky estimation.

Currently the only way we can do this is to use the `--checksky` option and use the statistics of the tiles used (before interpolation):

$ astnoisechisel image.fits --checksky --oneelempertile
$ sky=$(aststatistics image_sky.fits -hSKY --median)
$ astarithmetic image.fits $sky - --output=input-no-sky.fits

Mohammad Akhlaghi <makhlaghi>
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