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The 'annoying-noise-blob', Michael Timm

The 'annoying-noise-blob'

The 'annoying-noise-blob', Michael Timm

The 'annoying-noise-blob'

Description

This image shows my 'annoying-noise-blob'. It is a single flat frame without any correction (Version B shows the marked blob). I just did an automatic background extraction and stretched it to the max to show the problem. There is an elliptic area just right of the center where obscure noise lives. Why is that?

Image C shows a stacked image with flats, darks and bias (unprocessed, only background extraction and a stretch). I am pretty sure you can spot the noise blob.

Things are getting even weirder. After i saw this noise i cleaned my flatfield-box and retook the flats (images D and E showing the resulting MasterFlat). It seems that the blob has grown up while cleaning! I wonder what's wrong with my flats?

[Edit]: After i got a hint from Carsten in the comments below (thanks!) i took a few daylight flats with the shirt-method. Image G shows the poor result. The blob is there, sitting and waiting to eat the SNR of my lights :-( I wonder what possible sources are left? It is NOT the Lacerta flatfield box, it is - i think - nothing in my image train (would be otherwise spottable in the lights). So what's left? *sigh*

Comments

Revisions

  • Final
    The 'annoying-noise-blob', Michael Timm
    Original
  • The 'annoying-noise-blob', Michael Timm
    B
  • The 'annoying-noise-blob', Michael Timm
    D
  • The 'annoying-noise-blob', Michael Timm
    E
  • The 'annoying-noise-blob', Michael Timm
    G

B

Description: Noise blob marked.

Uploaded: ...

D

Description: MasterFlat with grown up noise blob.

Uploaded: ...

E

Description: MasterFlat with grown up and marked noise blob.

Uploaded: ...

G

Description: A daylight flat taken with a white shirt. The blob is clearly visible :-(

Uploaded: ...

Histogram

The 'annoying-noise-blob', Michael Timm