Imaging Jupiter

Now Jupiter & Saturn are rising at a respectable hour and getting a fairly good elevation, I have renewed my planetary imaging on these targets. Last summer’s apparition I only managed one half-decent IR image and really wanted a good shot in colour with the Great Red Spot visible. I would end up needing to learn a new piece of software for image de-rotation.

The Rig

Like with my planetary images last year of Mars, I’d be using the OMC-140 Maksutov-Cassegrain deluxe (5.5”) scope at 2000mm, f/14. Mounted on a tracking equatorial mount, I’d also use an Atmospheric Dispersion Corrector (ADC), Baader Flip Mirror (to help me locate the target by eye first), filter tray and ZWO ASI290MC colour camera. Image capture would be controlled by ASIAIR in video mode.

The Process

Planetary imaging involves a lot of stages and different software for each. The process I used is:

1. Shoot 3min video files at a high frame rate to give you around 10,000 images per file. I planned to shoot 10 video covering half an hour.

2. Process each video individually in Autostakkert (AS!3), combining the best 2,000 frames (or 1,000 if quality graph is poor).

3. Take the 10 stacked images into Registax and apply Wavelet sharpening to each.

It’s worth saying I’ve never reached this point before with what I would call ‘good data’. I normally pick the best frame after sharpening and do some final tweaks in PA and call it a day. But this time I had enough good sharpened frames to use WinJupos;

4. Bring each of the 10 sharpened images into WinJupos and assign the correct capture data (location, time etc.) and save each as a .ims image data file.
5. Load these 10x .ims files into the De-rotation menu and save the image. This - as far as I can tell - picks the middle of the images in time (unless otherwise specified) and makes a’ stack of the stacks’ based around that midpoint. The output image is sharper and less noisy than any of the individual .ims files. Save as TIFF (or other options).
6. Open your TIFF in PS to tweak your brightness, contrast, saturation etc.

Another bonis step you can do is open your 10x sharpened images as layers in PS and use the Timeline interface to create an animation from the frames. This can be outputted as a GIF to show the rotation over the 30mins.

First imaging session

I captured a set of images on 21st July. I didn’t even keep any to show as they were all garbage - out of focus and fuzzy. No amount of processing could salvage anything from what was basically poor data. I had also used a 1.3x barlow to try and push the focal length from 2000mm to 2600mm and this was a mistake as the conditions were not receptive to increased magnification. #EpicFail….but we learn move on.

Second imaging session

My second attempt was on Aug 28th. It was a clear Saturday evening and I set up to capture both Jupiter and Saturn. I ditched the barlow and just worked with the native 2000mm f/14 of the OMC-140. My plan was to try and image both in RGB colour and IR (IR tends to deliver sharper images) and then combine. This was still a bit of an experiment. I took more effort to focus and get the exposure correct and captured 10 video files each of 3mins (roughly 10,000 frames). Moon Io was in the frame too which made a nice composition. I then swapped filters and got spme IR videos too.

The image below shows the output from AS!3, followed by sharpening and post processing. The final image from the night is after running the sharpened Registax outputs through WinJupos. I also created an animated GIF of the individual frames.

As the frames with the IR685 filter were taken after the RGB, having process them I couldn’t find a way to match the features due to the speed of rotation. You can see below how far Io has moved in the comparison. Therefore the final image contained RGB only.

Third imaging session

The latest imaging session was the 6th September, and the most successful. I used SkySafari to plan when the GRS would be visible and this also coincided with a transit of Io followed by its shadow. I started imaging as the shadow sat directly above the GRS and continued for the next hour as the moon, then the shadow left the surface finishing in the arrangement seen below.

When I processed the images I found the first 6 videos (c.20 mins) were not great; probably a mixture of poor seeing as Jupiter was still low and the scope was maybe still cooling. Then the quality improved dramatically and the I got 14 good frames from 20.49pm to 21.27pm stacked and into WinJupos for de-rotation.

I’m very pleased with the image as it clearly shows cloud banding, the GRS and some finer detail. The animation shows it as a living, dynamic planet. I’ve definitely progressed beyond the fuzzy beachball stage and can trust in the methodology I’ve found through a lot of trial and error. I may now go back to the barlow when the seeing is good and try to see the impact of more magnification.