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

AC Her, CH Cyg, TX and AH Dra

We had a better night for observing last Saturday, the 17th September, when the sky cleared in the earlier part of the evening. Drifting light cloud was still a bit of an issue but not as much as on the 5th. Twilight ended just after 9pm BST when I started observing and the moon wasn't due to rise until 10:11pm BST it being at last quarter.

It was earlier enough that I could get a decent observation of AC Herculis before it began to head over to the west. At 19:52 UT I could make out star E on chart 048.04 and so my limiting magnitude was fainter than 8.2. At 20:09 UT I estimated that AC was about equal in brightness to star D which made it magnitude 7.4.

I then went on to look at CH Cygni which lies in the wingtip of Cygnus the swan and overhead at this time of the year. At 20:29 UT I estimated that CH was about equal in brightness to star A on chart 089.04 (pdf) which made it magnitude 6.5. I think my estimate may have been 0.2 to 0.3 magnitudes brighter than other BAA observers who saw this star on the same night.

I moved round to the other side of the house to have another go at TX and AH Draconis. At 21:11 UT I thought that TX was brighter than star N (mag. 7.7) on chart 106.03 but only somewhat fainter than star K (mag. 7.0). So my estimate was that it was 2 "points" from N and one from K making it magnitude 7.2.

Finally, at 21:28 I estimated that AH Dra was about midway in brightness between star 1 (mag. 7.1) on chart the same chart and star 6 (mag. 7.8) making it magnitude 7.5.

All text and images © Duncan Hale-Sutton 2022

TX and AH Draconis

It has been a difficult time to get any observing done recently what with the cloudy skies we have been experiencing of late. I tried a couple of times on the 19th and 31st August to do some variable star observing but cloud just kept getting in the way. I had some more success over a week ago on the 5th September and was able to get observations made of TX and AH Draconis. At the time when I was observing, the moon was 2 days past first quarter but low in the sky to the south. There was a little bit of light cloud but this didn't really make an impact until after 11pm BST. There is no problem with twilight now after 10pm BST when I started observing. These stars in the constellation of Draco aren't far from the star Eta Draconis which was still high in the sky to the west.

At 21:38 UT I could make out star P on BAA chart 106.03 with my 7x50 bins. This meant that my limiting magnitude was fainter than 8.4. At 21:46 I estimated that TX was marginally brighter than the star N (=7.7 mag.) on the chart but fainter than K (=7.0 mag.). So my estimate was K(2)V(1)N (one "point" from N but two "points" from K) which made it magnitude 7.5 to one decimal place.

Moving on to AH Dra I observed at 22:01 UT that this star was brighter than star 8 (=8.4 mag.) on the chart but fainter than star 1 (=7.1 mag.). In fact, it was much closer in brightness to 8 than it was to 1, so my estimate was 1(3)V(1)8 which made it magnitude 8.1 (to 1 d.p.).

This last observation was a bit rushed as I could see a bank of cloud moving in from the south which would end my night. However, I don't think either of these observations are in too much disagreement with other observers from the BAA.

All text and images © Duncan Hale-Sutton 2022