Capturing stills for stacking - not a video

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Astropete1959
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Joined: Thu Aug 26, 2021 7:30 pm

Capturing stills for stacking - not a video

#1

Post by Astropete1959 »

How do I get SharpCap to save stills of say Jupiter, for stacking - and not a video file??? I can only get a picture file if I save / capture one image??? Have I missed something? It's frustrating the hell out of me!
Regards
Peter
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oopfan
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Re: Capturing stills for stacking - not a video

#2

Post by oopfan »

Hi Peter,

Select "SER" output file format. It is a video file having a ".ser" file extension. Then download *free* PIPP to extract the individual frames for processing.

I made a how-to video here:
https://rumble.com/ve87ot-how-to-proces ... a-pro.html

I really pushed the processing for this video:
https://rumble.com/vh9k77-dark-moon.html

My 71mm telescope can't deliver the quality of an 8-inch scope but it does all right.

Brian
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turfpit
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Re: Capturing stills for stacking - not a video

#3

Post by turfpit »

Peter

As an experiment, I once captured 100 FITS frames of a full moon using an Atik 314E CCD camera. Exposure setting was 4ms. I stacked the FITS frames with Autostakkert 3 and sharpened the result with Registax 6. The same technique could be used for Jupiter.

single-FITS-frame.JPG
single-FITS-frame.JPG (77.22 KiB) Viewed 515 times

21_27_41_lapl5_ap779_Drizzle15 (2).jpg
21_27_41_lapl5_ap779_Drizzle15 (2).jpg (506.49 KiB) Viewed 515 times


I am curious as to why you would do this as the conventional process for lunar/planetary/solar imaging is to capture in SER video format, then stack (statistically throwing away the poorer quality frames) & sharpen using the tools I listed above.

Dave
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oopfan
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Re: Capturing stills for stacking - not a video

#4

Post by oopfan »

Dave,

I think I understand now. Peter wants to LiveStack individual frames of Jupiter. I'll leave it up to you to explain why that is a bad idea :D

Brian
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admin
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Re: Capturing stills for stacking - not a video

#5

Post by admin »

Hi,

so, to summarize, capturing decent images of the moon, sun and planets requires capturing hundreds or thousands of frames as video and then using a stacking application (for example Registax or AutoStakkert) that can read and process the video.

To summarize why...

We want to see fine detail, so we use high magnification (long focal length)
At high magnification, the turbulence of the atmosphere (seeing) affects the image significantly
Taking any sort of long exposure (more than a fraction of a second) means it will be blurred by the turbulence
Therefore we take short exposures, typically ~1/30s or less to make sure that each frame is minimally affected by this blurring
Short exposures don't collect much light, so we need to use high gain to see anything (especially for planets, not such a problem on moon/sun)
High gain makes the individual images noisy
To bring the noise back down to manageable levels, we need to stack lots of frames (100s) - tyipcally the best quality ones after capturing 1000s
We want to capture lots of frames quickly, so video is a much more suitable format than still images

Hope that makes sense and explains why capturing the planets as still images for stacking is something that just isn't done very much!

cheers,

Robin
Astropete1959
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Joined: Thu Aug 26, 2021 7:30 pm

Re: Capturing stills for stacking - not a video

#6

Post by Astropete1959 »

Thx for everyone's replies!
My next thought was - how do I capture stills for stacking from the video. You have all answered that :) Many thanks!
Peter
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