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Effect of Sky Background % when stacking

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#1 RogueZero

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Posted 05 July 2020 - 02:50 PM

What kind of effect does variance in sub-exposure sky background % have on the final stacked image? Should low background % be selected for in the same way that low FWHM is?

 

For example in my latest set of subs the sky background varies between 1.44% and 0.92% over the course of the night. Should I exclude a proportion of the higher % subs (all other things being equal) to improve quality of the final image?

 

Thanks



#2 sharkmelley

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Posted 05 July 2020 - 03:35 PM

Where do you see sky background % reported?  I'm not even sure what it means to measure sky background as a percentage.

 

I guess you are asking the question in the context of a particular processing package?

 

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#3 Stelios

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Posted 05 July 2020 - 03:43 PM

I also don't follow. What software is this and what is "sky background %?"



#4 SilverLitz

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Posted 05 July 2020 - 03:52 PM

DSS shows Sky Background



#5 sharkmelley

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Posted 05 July 2020 - 04:53 PM

I guess DSS is reporting sky background as a percentage of the saturation level.

 

In any case,  don't worry if the sky background changes slightly from exposure to exposure because it's quite normal.  But you may want to investigate any outliers to remove exposures affected by passing cloud or exposures that "misfired" in some way.

 

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#6 RogueZero

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Posted 05 July 2020 - 05:10 PM

Yes, sorry, this is in DSS. I thought sky background was a recognized stat as DSS shows it along with the other important stats.

 

Thanks

 

I wasn't sure if higher sky background values ended up reducing contrast or increasing noise.




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