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Old 12-02-2018, 11:32 PM
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How long exposure for dslr.

I hope to get up North before the horse head disappears and take as long an exposure as possible on the Nikon 5500 thru the 80 mm or the eight inch...
My question is how much is enought just in case I get a good run.
Is there a point that with the dslr I would be wasting my time...
Alex
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Old 13-02-2018, 03:18 AM
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OzEclipse (Joe Cali)
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Alex

Shoot some dark frames of varying exposure time at varying ISO settings. try to do this at the same sort of temp you'll shoot at outside at night. You'll soon see where the noise becomes too much to deal with.

Joe
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Old 13-02-2018, 08:49 AM
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Camelopardalis (Dunk)
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Alex it all depends on how dark your sky is. The darker the sky, the lower ISO you want to use to utilise the dynamic range available.

In summer, you probably want to find a compromise, as the longer the exposure the worse the thermal noise will get.

As a stab in the dark, I would dial it up to ISO1600 for 2, maybe 3, minutes and see how you go. When the weather cools down a bit, and if you have a really dark sky, Id try dialling it down a bit.

Just be aware that some sensors have their quirks - I think the sensor in the D5500 is the same as in my Fujifilm, and these Sony sensors have whats called high conversion gain mode, which kicks in above ISO800...and reduces read noise, and thus the all-important signal to noise ratio.
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Old 13-02-2018, 11:24 AM
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Thank you gentlemen.
I will start small and take baby steps.
I like 400 and 800 iso a d only recently used 1600.
And as to total exposure I will just do what I can as it is probably more the case will I get just one cloud free night.
Thanks again.
Alex
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Old 13-02-2018, 12:42 PM
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Camelopardalis (Dunk)
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Yeah just experiment and see what works best.

The sensor is a good one to be experimenting with
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Old 13-02-2018, 12:56 PM
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The quality of your mount & guiding also plays a part. Short, noisy subs with round stars are usually preferable to long subs with eggy stars and smeared details.

Cheers,
Rick.
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Old 13-02-2018, 01:12 PM
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Quote:
Originally Posted by RickS View Post
The quality of your mount & guiding also plays a part. Short, noisy subs with round stars are usually preferable to long subs with eggy stars and smeared details.

Cheers,
Rick.
Yes indeed I have been impressed with just 30 seconds what I can get away with.
Alex
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Old 13-02-2018, 01:35 PM
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Yes indeed I have been impressed with just 30 seconds what I can get away with.
Whatever works is good with me, Alex
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