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Short Jupiter - Io - shadow and GRS gif 9-18-21

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#1 dcaponeii

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Posted 19 September 2021 - 06:12 PM

These 2% stacks of 60 s captures were taken right at the end of last evening adventure in collimation.

 

2021-09-19-0527_7-DWC-L-Jup__M__AS_P2_lapl5_ap42_Drizzle15wA_pipp.gif

 

Here is a 10% stack of a 60s capture at f/12.  10,000 frames GAIN = 225, 6ms exposure.

 

2021-09-19-0531_5-DWC-L-Jup__M__AS_P10_lapl5_ap42_Drizzle15wAP.jpg


Edited by dcaponeii, 19 September 2021 - 06:23 PM.

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#2 Borodog

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Posted 19 September 2021 - 06:24 PM

I recall you saying that you thought that small stacks were helping you tame the astigmatism. Do you have a physical explanation for why that might be? My gut instinct is that small stacks may only have the appearance of being a bit sharper because they are noisier.



#3 dcaponeii

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Posted 19 September 2021 - 06:53 PM

I recall you saying that you thought that small stacks were helping you tame the astigmatism. Do you have a physical explanation for why that might be? My gut instinct is that small stacks may only have the appearance of being a bit sharper because they are noisier.


Seeing causes the image to move back and forth through the best focus point. As it does the image changes from, for example, the elliptical centroid vertically aligned over to the orthogonal direction. This is what causes the cruciform image during captures. By reducing the stack size we only get the images that are at or very near focus and avoiding the flaring that occurs inside or outside of focus. As you increase the stack sizes you can see the onset of these orthogonal flares at the larger stack sizes. I’ve been doing 1, 2, 5, and 10% stacks routinely and this is the typical occurrence except when, as Daryl noted in one of his comments, the seeing is excellent. In that case the flares don’t form until above 10% stacks.
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#4 Borodog

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Posted 19 September 2021 - 08:16 PM

Interesting. You should be able to test that. Image a star, as with collimation, Analyze it in AS, and check the individual frames at 1, 2, 5, 10, 20%, say. You should see whether your hypothesis is correct or not. Although, you may have already done this.


Edited by Borodog, 19 September 2021 - 08:17 PM.



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