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  • Writer's pictureStephen Strum

Celestron C90 Imaging Challenge

Updated: Jan 31, 2021

Yes, you can do planetary imaging with a small telescope.

On Friday, June 26, 2020, I decided to challenge myself and see what I could do in terms of planetary imaging with the most difficult imaging setup I could come up with. To be fair, I still used my ASI224MC camera with a Televue 2.5x Powermate, both of which are great pieces of equipment. But, I put those on a Celestron C90, a small, cheap, and lightweight Maksutov Cassegrain telescope, and then put all of that on a photo tripod and head. Ok, so the photo tripod and head was a Manfrotto 190X tripod with an XPro fluid head, a $300 mount setup which was more than stable enough for the C90. But, since I had no slow-motion controls or tracking available, imaging was nonetheless very challenging. The field of view with the ASI224MC attached to a Televue 2.5x Powermate is extremely small, and so keeping anything in that field of view is very challenging. Frequently it would take me a solid two minutes just to get one of the planets in a position to where I could let it drift across the camera's field of view for ten seconds or so.

What I did for each imaging attempt was to get one good drift of the planet across the camera field of view, and then for the next minute or two try to hold the planet in the center of the field of view using the panhandle. The resulting vibration made each of the planets bounce around like crazy across the field of view. I had a fast shutter speed set, on the order of 7ms or so, which kept my mount shakes from blurring each frame too much.

I was skeptical about how much good data I would get, but I still was able to stack about 40% of the frames in AutoStakkert2 with each planet. After applying wavelets and doing an RGB align in Registax, removing noise in Topaz Denoise, and then compositing the three images in Pixelmator, I was able to get the image at the top of this post. Overall, I think it turned out surprisingly well, given the setup. I'm impressed with what a C90 can do, and I'll try this again at some point soon using a tracking mount to see what I'm able to accomplish. With similar seeing and a tracking mount, I could probably stack 70% of the frames and get even nicer images.

The whole point was to show that you can still produce pretty nice planetary images without any kind of tracking mount or even slow-motion controls using a small telescope.

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