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Capture settings for Jupiter (still playing)

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#1 Tulloch

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Posted 21 May 2020 - 07:40 PM

Hi there, last time I imaged Jupiter I had a play around with the capture settings to see if I could optimise them for my C9.25 SCT on a Celestron Evolution mount, ASI224MC and TV 2.5x PowerMate (which actually gives me about 2x mag). 

 

Jupiter was nice and high, seeing was good, so I captured 3 x 3 minute video streams one after the other, with different frame rates and gain settings to keep the max histogram at about 50-60%. The settings I used are shown below, and the processing was performed exactly the same for each run. I tried stacking 5000 and 10000 frames from each stream, same sharpening in Registax and Photoshop but less work to make the images look "pretty".

 

Run     Gain      shutter      fps     Hist (max)   Start time  Total Frames

 1         315      4.933 ms   202      56%           04:36:31      36460

 2         248      10.00 ms   99        50%           04:39:46      18000

 3         346      3.329 ms   291      57%           04:44:14      52533

 

The side-by-side images for 5000 and 10000 frame stacks are below (50% larger than captured size). It appears that the seeing (or the focus) may have dropped for the third run, but it's clear that the amount of noise is significantly higher than for the other two. The 5000 frame stacks are certainly sharper than the 10000 frame stacks, but I was a bit surprised that the noise levels for Run 2 were so significantly lower than higher frame rate captures. I tried reducing the stack sizes for Run 2 even further (2500 and 1500 frames), but there was only a minor increase in sharpness at the expense of significantly increased noise.

 

Based on this test, it's a close call but it appears that Run 2 is giving me the best result, the lower gain levels obviously produce less noise but the shutter speed is still fast enough to give me good sub-frames with no additional "blurring". File size is also a lot lower with the slower shutter speed, which is not a good reason to use it, but it is a bonus. I might try 150 fps also, but it does appear that 100 fps is a good speed to run with Jupiter (for my setup, ymmv).

 

Andrew

Attached Thumbnails

  • 2020-05-15-1841_2-L-Jup_AS_F5000 speed comparison small.jpg
  • 2020-05-15-1841_2-L-Jup_AS_F10000 speed comparison small.jpg

Edited by Tulloch, 21 May 2020 - 07:41 PM.

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#2 Kokatha man

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Posted 21 May 2020 - 08:10 PM

There are small differences that I can see between the 100fps & 200fps images...but that's leaving aside how dynamic seeing is - it's a good night when you get consecutive images in exactly similar seeing conditions...& that also neglects focus changes which are very real Andrew...

 

I'm not quite sure what you mean by <"blurring"> because you could drop your fps to 50fps or lower & I suspect that the images/frames would not suffer...even lower btw - perhaps you mean "influenced negatively by the seeing in some way..?"  (I'm probably a bit sensitive to all those "rotational blurring" sillies that pop up here from time to time! lol.gif )

 

I don't have any experience with the 9.25 but am still a tad surprised that your images are 50% larger than capture scale..? (♎4700mm with a 2x barlow)

 

But good experimentation, even if I'm a bit puzzled & have reservations - we all need to find our own optimal approaches..! waytogo.gif

 

Apologies, I've taken the liberty to define some regions in the 200fps image where I think the detail is better than the 100fps image...my take anyway & of course yesmv*..!

 

* "your eyesight might vary" lol.gif but I'm not merely referring to heavy contrast per se, but actually fine definition btw...although some folks reckon I see things that don't exist..! lol.gif

 

AndrewsJoves.png

 

 

 

 


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#3 Tulloch

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Posted 21 May 2020 - 08:59 PM

There are small differences that I can see between the 100fps & 200fps images...but that's leaving aside how dynamic seeing is - it's a good night when you get consecutive images in exactly similar seeing conditions...& that also neglects focus changes which are very real Andrew...

 

I'm not quite sure what you mean by <"blurring"> because you could drop your fps to 50fps or lower & I suspect that the images/frames would not suffer...even lower btw - perhaps you mean "influenced negatively by the seeing in some way..?"  (I'm probably a bit sensitive to all those "rotational blurring" sillies that pop up here from time to time! lol.gif )

 

I don't have any experience with the 9.25 but am still a tad surprised that your images are 50% larger than capture scale..? (♎4700mm with a 2x barlow)

 

But good experimentation, even if I'm a bit puzzled & have reservations - we all need to find our own optimal approaches..! waytogo.gif

 

Apologies, I've taken the liberty to define some regions in the 200fps image where I think the detail is better than the 100fps image...my take anyway & of course yesmv*..!

 

* "your eyesight might vary" lol.gif but I'm not merely referring to heavy contrast per se, but actually fine definition btw...although some folks reckon I see things that don't exist..! lol.gif

 

attachicon.gifAndrewsJoves.png

Thanks Darryl, I didn't look too closely at the 10000 frame results as generally the 5000 frame stacks were better, and don't forget that the top 10000 frames in the 100fps stack is the "top" 66% of the total, while it's only 27% of the 200 fps level. I think the key comparison would be the 5000 frame result at 100fps (top 33%) with the 10000 frame stack at 200fps. I have shown these two in the image below, I'm struggling to see much of a difference, but I'd trust your eyes before mine.

 

By "blurring" I meant image motion due to the planet shifting in the FOV due to atmospheric effects, trying not to mention the phrase "freeze the seeing". When I used to use my DSLR, it had problems because it sampled at 30fps and blurring was significant in anything above a breath of wind with my relatively lightweight mount.

 

According to FC, I'm running at about 4900 mm, which is backed up by Jupiter's size at the time (42.5", I measured 277 pixels at the equator which equals f/21.5). The images show Jupiter at about 416 pixels wide = 150% capture size.

 

Andrew

Attached Thumbnails

  • 2020-05-15-1841_2-L-Jup_AS_5000-100 vs 10000-200 speed comparison small.png

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#4 sunnyday

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Posted 21 May 2020 - 09:08 PM

I prefer the run of 5000 frames and especially the 200 fps.
I find the details more marked, more visible.
thanks.


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#5 Kokatha man

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Posted 21 May 2020 - 10:08 PM

...in general I'm still seeing things a tad better in the 200fps image of Post #3 Andrew - but you are the person that has to be best-pleased, so that's where the final decisions lay! :)


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