bugGNU Astronomy Utilities - Bugs: bug #60644, Brightness error over-estimated in...

 
 

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bug #60644: Brightness error over-estimated in scaled noise (STD less than one)

Submitter:  Mohammad Akhlaghi <makhlaghi>
Submitted:  Thu 20 May 2021 01:03:57 AM UTC
   
 
Category:  MakeCatalog Severity:  3 - Normal
Item Group:  Output not reasonable Status:  Fixed
Privacy:  Public Assigned to:  makhlaghi
Open/Closed:  Closed

Thu 20 May 2021 01:16:28 AM UTC, comment #1: 

This bug is fixed in Commit 036ada1b9bce.

Mohammad Akhlaghi <makhlaghi>
Group administrator
Thu 20 May 2021 01:03:57 AM UTC, original submission:  

As explained Section 3.3 (S/N Equation Modiļ¬cations) of the NoiseChisel paper, when the image noise has a value that is less than 1, it means that the data are not in units of counts (they are often scaled to other units, like electrons/sec). However, even though it is scaled (multiplied by a factor) from the original counts, the original noise was Poisson noise, it just needs to be scaled back.

In MakeCatalog, we were applying this scaling when calculating the signal-to-noise ratio (and thus the magnitude error). However, it was missing in the raw Brightness error columns. So when the data are in very small units (like Janskies!) the brightness errors become larger than the brightness itself, even for very high S/N objects!

Mohammad Akhlaghi <makhlaghi>
Group administrator

 

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    Date Changed by Updated Field Previous Value => Replaced by
    2021-05-20 makhlaghi StatusIn Progress Fixed
        Open/ClosedOpen Closed

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