The Great Conjunction of Jupiter and Saturn, 21 December 2020

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I had planned to take a series of photographs of Saturn and Jupiter in the days before and after 21 December as the planets appeared to move closer together and then as they moved apart.

However, despite the sky being reasonably clear for several evenings before 21 December, there was always a layer of low clouds over the Vosges themselves. By dusk the elevation of the planets was only 10 degrees about the horizon and getting lower. The planets often appeared and the disappeared in that cloud but were often still covered in a light haze. On the day of the conjunction, 21 December, and for the following days, there was thick obscuring cloud. The next time I saw them (and last, because of clouds for the following week) was briefly on 26 December.

I took several hundred photos in total. Above is one from each of the nights Thursday-Sunday before the actual conjunction on the Monday and one on the following Friday. The second was taken at 1725, so in the dusk light. The third was taken just before 1800 and shows clouds. The fourth shows the closest I captured the planets with some moons of both Saturn and Jupiter and I’ve added a screenshot from the free Stellarium planetarium software http://stellarium.org/ which helps identify the moons. Saturn and the rings weren’t separately identifiable and just appeared as an oval (the 26 December photo is the best).

I was using my 75-300mm lens at 250-300mm. I tried different exposures as the planets seemed over-exposed, but that made no significant difference so I must be at the limit of resolution of the sensor/lens image for that length telephoto. I had to focus manually as autofocus does not work on many cameras for small objects at a distant near infinity (for autofocus the camera needed to be able to focus either side of the correct focus point). When turned on my camera was set to go to an “infinity” point (the setting is 999.9m) which gives a good depth of field but the primary focus is not at infinity (the latest top-of-the-range Olympus DSLR do have a new special Starry Sky autofocus, which reportedly works). The other problem was either the low haze or fine high cloud making the images fuzzy. I’ve since seen photos on an Olympus web site where someone used a 400mm lens and the rings and planet were separately identified.

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