Using the brain and amp glow

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cuivenion
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Using the brain and amp glow

Post by cuivenion » Thu Jan 31, 2019 10:30 pm

When using the brain function to measure sky brightness could it be thrown off by thermal noise or amp glow. Would it be advisable to use a dark frame during this procedure?

cuivenion
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Re: Using the brain and amp glow

Post by cuivenion » Fri Feb 01, 2019 2:21 pm

Anyone have an answer for this, I'll be setting up in a few hours. :)

BlackWikkett
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Re: Using the brain and amp glow

Post by BlackWikkett » Fri Feb 01, 2019 2:35 pm

Sorry I don't have an answer to this but I'm very curious to see what Robin has to say on the subject. Some of the cameras I use have very pronounced amp glow that must be showing up in the calculation of the sky brightness measurements the brain does. I'm sure we'll get an answer soon.

-Wikkett

cuivenion
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Re: Using the brain and amp glow

Post by cuivenion » Fri Feb 01, 2019 3:02 pm

I'm suspecting a well matched dark certainly won't do any harm.

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admin
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Re: Using the brain and amp glow

Post by admin » Fri Feb 01, 2019 8:02 pm

Hi,

I think the best option would be to select a sub region of the image away from the stronger amp glow regions for the sky brightness measurements.

Using a dark frame won't work for the sky brightness background measurement as the measurement procedure changes the exposure constantly to find a level that gives it a strong enough signal to work from – you wouldn't know in advance what length of dark frame to use. Additionally, using a dark frame would mean that any thermal noise would be removed from the image being assessed which would actually be a negative in this circumstance as we are trying to deal with how the sensor responds to the signal it sees without dark subtraction in our noise calculations.

Cheers, Robin

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Re: Using the brain and amp glow

Post by admin » Fri Feb 01, 2019 8:03 pm

Actually having just thought about this, I suppose I really ought to have the measurement procedure turn off dark and flat correction while measuring (if it doesn't already) as both could impact on the final measurement, although I expect that the size of the impact is not going to be too significant.

Cheers, Robin

cuivenion
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Re: Using the brain and amp glow

Post by cuivenion » Fri Feb 01, 2019 8:04 pm

Thanks Robin I'll bear it in mind.

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