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Dalriada n:
Kingdom of the Scots,
home of the residents

a shadow crosses Jupiter

This happens quite often. Solar eclipses on Jupiter occur when any of the natural satellites of Jupiter pass in front of the Sun as seen from the planet Jupiter. For bodies which appear smaller in angular diameter than the Sun, the proper term would be a transit. For bodies which are larger than the apparent size of the Sun, the proper term would be an occultation. There are 5 satellites capable of completely occulting the Sun: Amalthea, Io, Europa, Ganymede and Callisto. This month Sky at Night magazine alerted me: Friday April 17: This evening it is Callisto’s shadow that can be seen crossing Jupiter’s disk. The shadow starts to pass across the planet’s eastern limg at 22:15 BST and remains visible until 02:57. So I set up my kit to look out for it, using the webcam again, and the 2x Barlow lens.



The image below is from a movie clip I shot at 21:30. My image is not as good as Stellarium’s, as usual, but both show no shadow crossing Jupiter’s disk yet.

About an hour later, and having watched the news on TV, I shot another movie clip at 22:43. This time I think you can clearly see Callisto’s shadow in my image as well as Stellarium’s. Obviously I could photoshop the shadow to make it blacker and sharper like Stellarium’s but that might be ‘cheating’ (actually the line between ‘processing’ and ‘cheating’ is sometimes hard to draw in astrophotography).

After that I called it a night, I wasn’t about to wait until 02:57 to see the shadow safely off the other side – and it takes almost as long to pack the kit away as to set it up.