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Entire Io shadow transit time-lapse

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#1 Lopper

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Posted 27 July 2021 - 11:49 AM

I had been wanting to try to capture an entire shadow transit event for a long time and I finally decided to take a shot at it back on July 19. The seeing was pretty good and I could afford to be a zombie in the morning so I stayed out late and collected data as Io and its shadow raced across the face of Jupiter. I then compiled all of the data into a 21-frame time-lapse video that covers about 3 hr 15 min.

 

Here are the technical details:

 

I recorded 3 x 1.5 min captures of Jupiter for each frame in the time-lapse using my C9.25, 2.5X Powermate, and ASI224MC with UV/IR-cut filter (exposure 10 ms, gain 350). This gave a total of 63 video files. Each group of 3 captures was started 5 minutes after the previous capture ended. The 5 minute gaps gave me a chance to offload the data to a portable hard drive (251 GB of data in total...way too much to fit on my laptop's HD) and remove dew from the corrector plate of my C9.25 with a hair dryer (I should probably invest in either a dew strip or a dew shield).

 

I stacked the best 25% of the frames from each of the 63 individual video files in AS3 with alignment points distributed all across the face of Jupiter. I used a 3x drizzle for those stacks. I then repeated the stacking using a single alignment point on Io for any video in which Io was either off to one side of Jupiter, on Jupiter's limb, or just inside Jupiter's limb. I used a 3x drizzle for those stacks, too. The total AS3 processing time was about 9 hours.

 

For processing, I resized each stack back to its original capture size and performed deconvolution in Fitswork4. I used different deconvolution settings for Jupiter than I did for Io. I color balanced those images and gave them a very gentle wavelet sharpening in Registax6, then adjusted the contrast and saturation and performed noise reduction in Image Analyzer.

 

I then derotated and combined each group of 3 images into a single image in Winjupos. This caused Io to get smeared out for all of the images in which Io was not directly in front of Jupiter. For those images, I transposed the separately processed Io image onto the corresponding derotated Jupiter image.

 

The result of all of that was 21 individual images, each of which would become a frame in the time-lapse. Lastly, I touched up the brightness of the individual images in GIMP and then stitched them together to make a time-lapse video.

 

Here's the YouTube link if you'd like to check it out.

 

I've included a few of the frames of the time-lapse below. The seeing improved as the night wore on and Jupiter rose higher in the sky.

 

This turned out to be a really fun (albeit time-consuming) project. Thanks for looking!

 

Matt

 

Io Shadow Transit Frame 03.png

 

Io Shadow Transit Frame 10.png

 

Io Shadow Transit Frame 14.png

 

Io Shadow Transit Frame 20.png


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#2 Daveatvt01

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Posted 27 July 2021 - 01:02 PM

Very neat!


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#3 KiwiRay

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Posted 27 July 2021 - 01:07 PM

That's an enormous amount of work, but something I can appreciate having once done a 23-frame animation (although based on just 23 recordings and no WinJUPOS derotations). Those later frames above look very good, but unfortunately the upload to YouTube appears to have compressed the file in some way, and much of the quality is lost. Not that I'd want you to do even more work, but it might be better to create an animated image file, like a gif or apng.


Edited by KiwiRay, 27 July 2021 - 01:07 PM.

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#4 Lopper

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Posted 27 July 2021 - 02:23 PM

That's an enormous amount of work, but something I can appreciate having once done a 23-frame animation (although based on just 23 recordings and no WinJUPOS derotations). Those later frames above look very good, but unfortunately the upload to YouTube appears to have compressed the file in some way, and much of the quality is lost. Not that I'd want you to do even more work, but it might be better to create an animated image file, like a gif or apng.

I agree with you on the loss of quality from the YouTube compression. I wish I knew of a way to avoid that from happening. I made an animated gif from the individual images but the file size was larger than the CN posting limit. I've never made an animated png before. Maybe I can figure out how to do that.



#5 KiwiRay

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Posted 27 July 2021 - 02:37 PM

I've had to upload larger animations elsewhere and link to them as you did above. I have a flickr account, which does allow gifs to be uploaded and then linked to. Even though flickr doesn't display gif files as animated files in the main image window, you can view the original file in the downloads window and copy that link.

 

Here's an example:

 

https://www.flickr.c...57663518058208/

 

Click on the download link at bottom right, select View All Sizes, and you'll see the original animated gif, the link to which I copied and pasted in the image description. Clumsy, but it works well for sharing on CN.


Edited by KiwiRay, 27 July 2021 - 02:43 PM.

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#6 R Botero

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Posted 28 July 2021 - 03:40 AM

Excellent result :cool: Great work :waytogo:
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#7 Lopper

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Posted 28 July 2021 - 10:23 AM

I've had to upload larger animations elsewhere and link to them as you did above. I have a flickr account, which does allow gifs to be uploaded and then linked to. Even though flickr doesn't display gif files as animated files in the main image window, you can view the original file in the downloads window and copy that link.

 

Here's an example:

 

https://www.flickr.c...57663518058208/

 

Click on the download link at bottom right, select View All Sizes, and you'll see the original animated gif, the link to which I copied and pasted in the image description. Clumsy, but it works well for sharing on CN.

Thanks for describing that, it had not occurred to me to try flickr. And that animation you linked to is fantastic! It really captures the three dimensionality of Jupiter and its moons.



#8 mrflibbles

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Posted 28 July 2021 - 01:21 PM

Very nice, I left a comment on Youtube as well.


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