Author Topic: Bias,Dark,Flats artifact removal question  (Read 518 times)

Offline CraigNZ

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Bias,Dark,Flats artifact removal question
« on: 2018 February 01 11:26:18 »
Is there a process or script which can scan a collection of Bias, Dark or Flat frames and remove artifacts that appear in only one frame but not others.  For example, if there is a cosmic ray hit at a location on one image but does not appear on subsequent images then the damaged pixels could be repaired using the surrounding pixels or pixels from subsequent images.  This method would insure hot pixels, which appear in each image, are correctly allowed for and not simply removed.

Offline ngc1535

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Re: Bias,Dark,Flats artifact removal question
« Reply #1 on: 2018 February 01 12:18:36 »
Hi Craig,

When you use ImageIntegration this statistical rejection takes place when you create master calibration files or combine light frames. You get to set the degree of rejection by choosing the rejection algorithm and adjusting the sigma rejection thresholds. BPP (since it uses ImageIntegration) permits you the same options. Hotpixels would not be removed by this statistical rejection- because as you say, they are in each bias, dark, and flat. (They would go away for the lights if you dither your data and align on a light signal, thereby shifting the original pixel array).

(Static) Hot pixels then are really only "removed" by measuring their deviation in intensity compared to neighboring pixels- or by a map you create. But this is a separate process (CosmeticCorrection or DefectMap). It seems for your question you thought it was an all-in-one thing?

Just using ImageIntegration (or BPP Calibrate Only with no CosmeticCorrection) and I think you get what you want.

-adam

Offline CraigNZ

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Re: Bias,Dark,Flats artifact removal question
« Reply #2 on: 2018 February 02 01:47:51 »
Hi Adam,

Thank you for the detailed reply.  I will run some tests using the methods from your reply.  I have some dark frames that have cosmic ray hits on a few images, I'll check to see that they are removed and not contributing to the Master Dark.

Craig