Jupiter

A few days ago on Monday the 19th September we had some very nice dark skies and I thought I would try to observe Jupiter which is approaching opposition on the 26th September. I decided to use my 5.5 inch Orion OMC-140 Maksutov-Cassegrain mounted on a Sky-Watcher HEQ-5 mount. I didn't bother to set up the drive properly so the image of the planet drifted in the eyepiece.

At about 11pm BST I began using a Celestron 25mm eyepiece which gave a magnification of 80x as the scope has a focal length of 2000mm. It was nice to see all four Galilean moons and some details on the planet surface. Rather than trying to photograph what I could see I made a drawing:-

In this picture south is up and west is to the left. The moons were nicely displayed with Io closest to Jupiter and then, with increasing distance from the planet, Europa, Ganymede and Callisto in that order. This was verified by looking at the BAA Handbook. On the planet itself the Northern Equatorial Belt (the much darker thicker line) was obvious but the detail of the southern features much less so and my impression was of three faint lines as drawn. I swapped to a 20mm Erfle lens which gave a slightly better view (x100) whilst I drew the details.

I wish I could have seen more details on the gaseous surface but I think a 5.5inch objective just isn't big enough. I did swap to a 9mm orthoscopic eyepiece that gave a magnification of x222 but this didn't improve the detail, though I did look very hard. The seeing was pretty good and there were longish periods when the image looked stable and in focus. I finished observing about 40 minutes later.

All text and images © Duncan Hale-Sutton 2022