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Not enough integration?

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#1 physics911

physics911

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Posted 16 May 2018 - 05:00 PM

I had more noise than I thought I should have in the M51 I shot last weekend.

I shot 2 hours of lum, and 45 minutes each of RGB with an ASI1600 at -15C, bin 1x1, and unit gain.

I processed with plenty of darks, bias, and flats.

 

Is that just not enough time to get a smooth background?

 

Thank you,

Chris

 



#2 pbkoden

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Posted 16 May 2018 - 05:39 PM

There are a lot of factors to determine signal to noise for a certain integration time. What is your sky quality (light pollution), what is your aperture and focal length?

 

Imaging from a red zone, SQM-L reading in the mid 18's, I captured 8 hours of luminance and 4.5 hours of RGB (1.5 hours each) to get an SNR I was happy with on M51. This is with an 8" scope at 800mm focal length (f/4). Someone at a dark site could do the same thing in an hour. 



#3 Ishtim

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Posted 16 May 2018 - 05:51 PM

Optimize the exposure time for your subs. Lots of CN discussion regarding this.  Your f/4 scope should allow you do collect many exposures and achieve a decent SNR relatively quickly.     



#4 physics911

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Posted 16 May 2018 - 06:05 PM

My site is SQM 21.56, per a popular website, basically a class 4 Bortle, and I buy that based on observation.  So, while not perfect, I do have some decent skies.

My scope that night was an AT6IN reflector at 610mm, f/4, giving an image scale of 1.28"/px.




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