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

[Mohammad Akhlaghi]

URL:
  <https://savannah.gnu.org/task/?16239>

                 Summary: NoiseChisel option to avoid interpolation for
thresholds or Sky
                 Project: GNU Astronomy Utilities
               Submitter: makhlaghi
               Submitted: Sat 30 Jul 2022 04:18:35 PM BST
         Should Start On: Sat 30 Jul 2022 12:00:00 AM BST
   Should be Finished on: Sat 30 Jul 2022 12:00:00 AM BST
                Category: NoiseChisel
                Priority: 5 - Normal
              Item Group: Enhancement
                  Status: Postponed
                 Privacy: Public
        Percent Complete: 0%
             Assigned to: makhlaghi
             Open/Closed: Open
         Discussion Lock: Any
                  Effort: 0.00


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Follow-up Comments:


-------------------------------------------------------
Date: Sat 30 Jul 2022 04:18:35 PM BST By: Mohammad Akhlaghi <makhlaghi>
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








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