Live Stack With Planetary Images

Discussions of using SharpCap for Planetary Imaging
Zubenelgenubi
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Live Stack With Planetary Images

Post by Zubenelgenubi » Sat Aug 04, 2018 4:46 pm

Does SharpCap have the capability to Live Stack Planetary images?

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Re: Live Stack With Planetary Images

Post by admin » Sat Aug 04, 2018 6:51 pm

Hi,

no, this is not supported - the calculations to perform live stacking for deep sky typically take from 0.25s to several seconds (depending on resolution). This is far too slow for planetary imaging where you want to be running at about 30fps. The only real stacking option for planetary imaging is to capture a video and stack afterwards. Maybe when computers get another 10 times faster or so we can try live planetary stacking!

cheesr,

Robin

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Re: Live Stack With Planetary Images

Post by Hibou » Sat Aug 04, 2018 7:15 pm

I think you can already do it if you switch off "Align frames", and as Robin says if your computer is fast enough and your frame rate slow enough. It is useful for non-astronomical imaging to see the image build up in real time, but then my frame rates are much less than 30fps and my FOV is steady.
Alan.

Zubenelgenubi
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Re: Live Stack With Planetary Images

Post by Zubenelgenubi » Sun Aug 05, 2018 12:01 am

Thanks for the prompt responses. I am blown away by the Live Stack mode for DSO. Live Stacking is a bit hit at our outreach pblic viewing sessions. I know that planetary Live Stack would be challenging but boy if you could pull it off...….

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Re: Live Stack With Planetary Images

Post by Ian » Tue Jul 21, 2020 9:57 pm

Hi Robin

Understood that live stack with planetary images for EAA is a technical hurdle. We should note also that pc power has increased massively with AMD 12core now around $500. Unthinkable only a couple years ago!

Researching this issue, I came across a two year old post by geminijk in CN forum, so would be interested in what you think.

The very interesting thing is a long time ago, using a Meade DSI II color camera and Meads Envisage, all I had to do was draw the alignment box around Jupiter, and get a stacked, aligned and thus sharpened image in a few seconds. No it wasn't like doing a full stack for AS!2 or Registax, but still darn good for getting a MUCH improved image. If the Meade Envisage could do that then (8ish years ago), why can't Sharpcap have similar capabilities added?

Also, when I used to use mallincam's and the Miloslic software, there was a limited stacking feature available for planets, it is called "video stacking"

All the best
Ian
Shambhala Observatory

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Re: Live Stack With Planetary Images

Post by admin » Wed Jul 22, 2020 7:06 pm

Hi,

I think that you're right that the processing power is probably available on high end PCs, at least, for a simple stacking approach that would use the centre of brightness of each image for alignment (the more complicated stacking used in applications like AS!2 does feature detection and - I think - stretching of the image to compensate for atmospheric movements... That may still be too expensive to run in real time).

I don't know how much improvement such as simple stacking procedure would bring to the final image – it would certainly bring down the noise levels but would it enhance or smear out the detail? How would the stacked image respond to sharpening?

If anyone wants to post some planetary capture SER files online and share links here, then I would be tempted to do some experiments when I have some spare time.

Cheers, Robin

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Re: Live Stack With Planetary Images

Post by turfpit » Wed Jul 22, 2020 7:44 pm

Robin

I have sent you a Dropbox link to a Jupiter (72 fps) & Saturn (39 fps) SER file for your development testing. ASI120MC, RAW8, 640x480.

DFave

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Re: Live Stack With Planetary Images

Post by admin » Thu Jul 23, 2020 4:44 pm

Thanks Dave,

this isn't something I expect to be able to get any progress on straightaway as I have plenty of other SharpCap work lined up for the moment, but I will stash the files to use when I do have some time to look at this.

Cheers, Robin

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Re: Live Stack With Planetary Images

Post by RonAM » Fri Jul 24, 2020 1:15 am

I want to echo the enthusiasm expressed in the original post. My neighbors were treated (me too) to a beautiful live view of Neowise during livestack where they could see it on the computer screen, and then look to that part of the sky and not see it except with binoculars. They were blown away.

Regarding planetary, correct me if I’m wrong but I understand there are 2 reasons for fast frame rates: 1. Brightness of the planets requires short exposure times and 2. Atmospheric turbulence opens brief sub-second moments of good seeing that are fleeting. Of course for a fast rotating planet like Jupiter the features shift within a few minutes as well. But what about this idea: use a neutral density filter to allow longer exposure times (say 500-1500 milliseconds), and then livestack 30 frames or so over a half minute time....It would have to be very good seeing with minimal atmospheric turbulence, and a strongly dimming filter to cut intensity by 10-100x to allow for longer exposure time.

Does this have merit, or not?

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Re: Live Stack With Planetary Images

Post by admin » Fri Jul 24, 2020 4:35 pm

Hi,

if you wanted to take longer exposures of planets, turning down the gain of the camera would probably be sufficient to allow fairly long exposures without saturating (normally we turn up the gain quite a lot to allow the short exposures). However taking these long exposures negates the advantage of 'lucky imaging' where the capture of many short frames allows us to find some frames where the atmospheric turbulence is not distorting the image. This means that taking lots of short frames is really the only way to go.

Cheers, Robin

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