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PI Rejection Low seems to include image data

astrophotography beginner dso
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#1 bjm

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Posted 01 June 2020 - 01:16 PM

Hi,

See attached stretched images of M16.  I understand the high rejection seems to have done its job, contrails gone etc.  But the low rejection data seems to include information that would be valuable for the light frames.  I took this with a ZWO183MC and used BPP in PI with standard settings.  

 

How to I tweak the settings so this data isn't rejected.  It seems that some of the baby is being thrown out with the bathwater!

 

Thanks again for all of your help.

 

Love CN!

 

Brian

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#2 Peregrinatum

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Posted 01 June 2020 - 05:55 PM

I think you add a pedestal during calibration, then take it out during integration... I don't think you can add/subtract a pedestal in BPP


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#3 ChrisWhite

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Posted 01 June 2020 - 09:12 PM

Raise the "sigma low" value under "pixel rejection(2)" section.

Edit- I see you are using bpp. I don't use bpp but rather manually calibrate, register and integrate. If there is a setting in bpp for sigma low... raise the value.

Edited by ChrisWhite, 01 June 2020 - 09:14 PM.

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#4 bobzeq25

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Posted 01 June 2020 - 11:02 PM

I use a pedestal when I have the problem.  Not often.  Usually it's with narrowband.

 

Tips.  You need to calibrate step by step to do it.  You add it in ImageCalibration.

 

Typical PI murkiness.  You do _not_ use the Pedestal subsection (which is for removing a pedestal added by the camera, I have no clue when that is an issue), you use the Output Pedestal setting in Output.

 

You don't have to do anything to remove it, PI does that automatically later.

 

100-200 is a good setting.



#5 bjm

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Posted 23 June 2020 - 10:42 AM

Thanks to all for your help.  Been too busy to revisit this but will try and let you know how it goes.



#6 Peregrinatum

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Posted 23 June 2020 - 10:53 AM

Another thing to check are the "low rejection" maps in PI, experiment at which sigma low settings gives you an acceptable level of rejection your are looking for



#7 ChrisWhite

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Posted 23 June 2020 - 08:49 PM

Raise the sigma rejection value for low.


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