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How do I determine the optimal imaging duration with light polluted skies

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#1 markfeastman

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Posted 02 December 2019 - 12:47 PM

I live in Murrieta Ca and the light pollution maps I can find are from 2015 indicating that I am in Bortle 5 skies. We are surrounded by new developments and I have 2 yellow street lights less than 100 yards from my backyard.  So it seems the light pollution is worse than Bortle 5.

I can barely see any of the Milkyway at the zenith....so I think it's actually ~ Bortle 7

 

My questions is how long should I image to get the best SN ratio in stacked images?

 

Equipment:

Takahashi FSQ 106 (530 mm FL)

Takahashi FS-60Q (600 mm FL)

Starlight Xpress 25c

Canon 6D

Losmandy G11 Gemini 2

Filters:

Optolong L-Pro

Astronomic UHC

 

Thanks



#2 f430

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Posted 02 December 2019 - 12:58 PM

I initially judge by the ADU value of the medium / medium large sized stars in the image. 



#3 markfeastman

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Posted 02 December 2019 - 01:03 PM

I initially judge by the ADU value of the medium / medium large sized stars in the image. 

Thanks John, can you elaborate?  

How do I use the ADU on the medium-sized stars to determine the optimal imaging duration?



#4 zxx

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Posted 02 December 2019 - 01:17 PM

On the histogram , have the data spike about 30% from the left.  I get 2 min from my red zone at iso 800 at 480mm.

 I shoot for at least 50 subs , 150 is better.


Edited by zxx, 02 December 2019 - 01:20 PM.


#5 Jim Waters

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Posted 02 December 2019 - 01:51 PM

For the Canon 6D I expose until the histogram is between 20 to 25% max.




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