5 min reading
Recently the weather has been atypically English, ie absolutely appalling. I say “recently”, but in fairness it feels closer to about 865 million years. There’s been no chance to do much of anything, and on the very rare clear(ish) nights the Long Covid has had its hold on me so I haven’t been able to get out and do any imaging anyway.
Last weekend though I had a clear spell forecast for Friday night. Now other than a night out with my partner, Amanda, this is my idea of a night out. As is atypical for the UK the forecast all night clear sky ended up being two hours worth. But despite the “ten tenths cloud over the target” as the boys in Bomber Command would often be heard to say during the war, it was an amazing two hours that resulted in my best Jupiter to date.
It’s nowhere near what you’d see from the likes of Damain Peach or Ivana Peranic, both of whom do some amazing work in planetary imaging (and you REALLY need to check them out), but for me it’s a huge win because it shows I’m on the right track with my own.
One of the biggest personal issues I have with mine is that I’ve not invested the time in it like I do with DSO (deep space objects) work, and that’s because it’s a completely different beast, both in the capture and the processing.
The Differences Between DSO and Planetary
With DSO it’s all about sinking as much acquisition time with long sub frames into capturing the data, and then spending hours stacking and teasing the detail out. The targets are inherently dim, which is why we put the time into it that we do, and frequently we have to capture many hours of data to produce an image we’re even vaguely happy with.
The planets however are a lot brighter, and because they’re small bodies with a high rotation period longer sub frames (or subs) won’t work. So how do we do it? The easiest, and best, way is to capture them using video. If you understand anything about video then you know that all a video is is a collection of short frames put together in order to show movement over time.
But we don’t necessarily want to actually show any movement on a planet surface (unless that’s the actual point of the video of course) so we need to keep the videos short enough so that the planet rotation doesn’t appear. In the case of Jupiter, with a high rotation period of 10 hours (the time it takes for the planet to make one complete rotation), it means keeping the videos to around two minutes. But you can capture a lot of frames in two minutes!
We then take that video, feed it into some software for it to be analysed, and then the best frames from that video are extracted and then stacked together to produce a final cleaner and sharper image, which is then processed manually in more software to improve further on it.
An inherent problem as well with planetary imaging is we’re often using much longer focal length telescopes, and as such the effects of atmospheric disturbances are greater, as is the amount of wobble if you touch the scope to adjust focus. You can see this effect yourself just using a pair of binoculars looking at terrestrial objects, especially on a warm day.
The Final Image
For this one I used a Maksutov 102mm telescope with a focal length of 1300mm, a x2 Barlow lens which brought the focal length up to 2600mm, an atmospheric dispersion corrector that corrects for light dispersion created by the different wavelengths of light being refracted by our own atmosphere, and the Altair GPCam2 224C planetary camera.
The Barlow is certainly the weakest link in this imaging chain, being a cheap bog-standard Celestron one, but I do have a 2 inch one with ED glass that I’m going to try and figure out a way of incorporating in. I also can’t get the higher frame rates with the Hypercam that I’d be able to get with a dedicated planetary camera, so I’m on the lookout for one that won’t break the bank. It’s low priority for now though, especially in a cost of living (or even existing) crisis.
So here’s my image of Jupiter, captured from the front garden at my kids home, with the added bonus of the moon Io (pronounced eye-oh) and its shadow on the surface of Jupiter. Thanks for reading, and clear skies all.
Update 10th Dec 2022
Couple of updates on this; I’ve since discovered that we weren’t working at 2600mm. The barlow was in, however because I’d been using it to serve as an extension, I’d removed the glass, and forgotten to put it back in. Obviously I’ve since lost that piece. So we’ve actually been working at the native 1300mm.
The other update is that we’ve had another session and this time Millie managed to capture the GRS, or Great Red Spot, the largest storm in the solar system at over 10,000 miles in width and with wind speeds exceeding 260mph!