Question about the Smart Histogram (The Brain)

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Blade71
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Re: Question about the Smart Histogram (The Brain)

#21

Post by Blade71 »

Hi Robin,

A follow up question, sky/seeing conditions change often, so how often would it be recommended or necessary to the run the brain get any updated recommendations on exposure time/gain?

Thanks!
Eric
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admin
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Re: Question about the Smart Histogram (The Brain)

#22

Post by admin »

Hi,

If the sky brightness increases, but you are not having any problems with tracking/guiding then you haven't got anything pushing you towards the shorter exposures that you could use in theory with a brighter sky, so there is no need to make adjustments. This might be the case if you move to a different target that is nearer the horizon or nearer the moon for instance.

If the sky brightness decreases then you need to be a bit more careful – you could need to use longer exposures to get the best results. This might be the case if you move to a target nearer the zenith or further from the moon. Typically you can get a feel for whether this is required by keeping an eye on the histogram peak levels of your image frames – these are really measuring the sky brightness too. If you have been getting 20% histogram peaks with 60s exposures in one area and then you move to another area where the same exposure gives the histogram peak at 15% then you should probably remeasure (and may find that the recommended exposure has nearly doubled). If the histogram peak only changes slightly to say 19% then there's probably not much point in remeasuring.

Cheers, Robin
austinstephens
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Joined: Sun Mar 28, 2021 3:02 pm

Re: Question about the Smart Histogram (The Brain)

#23

Post by austinstephens »

Hello Robin,
I love using the Brain/Smart Histogram. It's a fantastic feature. This is related to the last question asked by Eric. So, if my target moves from closer to the horizon to the zenith during imaging... would it be advisable to do the measurement at the zenith and use those settings (since, usually) that would mean less photons/px/sec? Or, is that just me trying to be lazy? :)

Thank you so much, Robin,
-Austin
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Re: Question about the Smart Histogram (The Brain)

#24

Post by admin »

Hi Austin,

as your target moves towards the zenith you usually get a darker sky, which would mean a longer recommended exposure time. You can certainly deal with this by measuring at the zenith to begin with - this will recommend a longer time, but will do no harm as long as it is within the capabilities of your mount/guiding.

cheers,

Robin
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