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Looking for a guide on how to read an astrophotography histogram!

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#1 zigee

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Posted 28 February 2020 - 03:33 PM

I'm a post processing noob, and would love to understand how to truly understand and read an astro histogram. I see things on forums and other sites about clipping, etc., but I haven't been able to find something that I can understand... any insights from the CN community for how to read a histogram?

 

 



#2 bobzeq25

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Posted 28 February 2020 - 04:21 PM

The key thing is to be sure you have a linear one, unless you use a DSLR.

 

Good sources of one are PixInsight (of course <smile>) and IRIS, which requires some fiddling with the scales.

 

There'll be an obvious skyfog peak.  Assuming you can convert ADU to electrons, a good way to limit clipping is this.

 

Convert the skyfog peak to electrons.  Subtract the ADU of a bias (or dark flat, doesn't matter).

 

Calculate your read noise squared. (it will be in electrons squared, ignore that).

 

Keep the first number in the range of 5-10 times the second, and the amount of clipping will be reasonable.


Edited by bobzeq25, 28 February 2020 - 04:22 PM.


#3 kathyastro

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Posted 28 February 2020 - 04:29 PM

Assuming you can convert ADU to electrons

Hmm...  Given that the OP was asking for a basic understanding of histograms, this assumption may be asking a bit much.


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#4 scottmm2012

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Posted 28 February 2020 - 04:36 PM

Have you watched this video. 

Garrett does a good job making it pretty simple.

 



#5 bmhjr

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Posted 28 February 2020 - 05:28 PM

Jon Rista has a good histogram explanation:

 

https://jonrista.com...and-histograms/



#6 bobzeq25

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Posted 28 February 2020 - 06:52 PM

Hmm...  Given that the OP was asking for a basic understanding of histograms, this assumption may be asking a bit much.

If he has a ZWO camera, it's a ridiculously simple graph on the home page for that camera.

 

It does take some research otherwise, but it's quite doable.  Google <camera> <electrons> <ADU>.

 

Jon Rista has a good histogram explanation:

 

https://jonrista.com...and-histograms/

That is excellent.
 


Edited by bobzeq25, 28 February 2020 - 06:52 PM.


#7 zigee

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Posted 02 March 2020 - 02:04 AM

If he has a ZWO camera, it's a ridiculously simple graph on the home page for that camera.

 

It does take some research otherwise, but it's quite doable.  Google <camera> <electrons> <ADU>.

 

That is excellent.
 

i just got my first ZWO camera!

 

 

Jon Rista has a good histogram explanation:

 

https://jonrista.com...and-histograms/

 

absorbing this like a sponge... thank you!


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