Great Conjunction on 2020-12-23

Posted by Rod Pommier
on Tuesday, December 29, 2020
I finally got one clear night on 2020-12-23 with which to view and photograph the Grand Conjunction. It was two nights past minimum separation, but both planets still fit on the DSLR camera chip at prime focus of my 8" SCT. Conditions were not good. The planets were only 9 degrees above the horizon, gusting winds shook the telescope, and seeing was mediocre. I shot scores of exposures of different durations, most of them using the "hat trick" to prevent shutter motion further blurring images.
This is a composite image of the best frames stacked and processed in various groupings to bring out different objects and combined back into a single image portraying the telescopic view. I stacked the best long exposures to display three Galilean satellites (Europa was transiting). I then added in lower quality long exposures to boost the signal to noise ratio high enough to bring out Titan. I did not have enough good long exposures to bring out Saturn's fainter moon Rhea. Exposing longer simply increased the probability the wind would gust and shake the telescope, completely ruining the exposure. I stacked the only 2 frames shot that night which showed Saturn's globe and rings decently. Jupiter was so bright at prime focus that very short mechanical shutter exposures captured it without significant vibration on many frames. I was very glad to have seen this rare Grand Conjunction through the telescope.

Image Data:
Telescope/Mount: Celestron Super C8 Plus at with Byers drive at f/10.
Camera: Canon EOS 20D, ISO 100, various exposures.
Location: Portland, Oregon, USA.
Date/Time: 2020-12-23, 17:00-18:00 PST.
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