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Lucky imaging parameters

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#1 MLM

MLM

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Posted 05 August 2021 - 09:59 PM

I've wondered about this for a while. What is the frequency that atmospheric distortions impact lucky imaging for planetary astrophotography?

 

For example, would a movie of 1000 frames, each 1ms exposure, total duration1 s, be a better or worse strategy than a 100 frame movie with 10 ms exposures, same total duration 1 s? Alternatively, one could capture 1000 x 1 ms frames, but at a lower frequency, say 1/10 x for an exposure range alos covering 10 s.

 

The underlying issue follows: Is it better to acquire a quick burst of frames in a short period, which I guess assumes that atmospheric distortion is occurring on a fast time scale; or should the total exposure be spread over a longer period, which I guess implies that atmospheric distortion is occurring over a longer period. I have no clue how to find out about this either in general, nor for my home suite,

 

Thanks

MLM



#2 luxo II

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Posted 15 August 2021 - 08:54 PM

This depends on your seeing, and the sensor pixel scale (arcsec/pixel) and aperture of the scope vs the scale of the turbulence cells, and its speed.

 

With the fast jittery turbulence we seem to have here this week, on the moon using my 6" mak at 1800mm, even at millisecond exposures and running at about 200fps, maybe 1 frame in 20 isn't blurred the rest are pretty awful. 

 

There are occasions when - even in my 10" at 3m focal length, the seeing is like slow-moving waves, with a period of a second or more, sometimes even still... in those conditions its obviously easier to get a high percentage of good frames with exposures at say 100 milliseconds.

 

But this year has been abysmal...


Edited by luxo II, 15 August 2021 - 09:12 PM.

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