Four variable stars in Draco and Ursa Major (9th January 2024)

Earlier this week we had a couple of nights of very cold clear weather. On Tuesday the 9th January the moon was 2 days before new and astronomical twilight ended at 18:15 UT. I went out early evening to do a bit of variable star observing. Even though I was well wrapped up it felt exceptionally cold as the temperature was only a few degrees above freezing and there was a bit of a wind. Still, the cold clear air meant that the sky looked stunning especially as Orion began to rise over the tree tops.

I thought I would start with the two stars I monitor in Draco as they were beginning to become low down in the north west (even though they are circumpolar). Using my 7x50 binoculars I began with TX Dra which is found on chart 106.04 of the BAA. TX is always easy to find. Firstly, you look for the Little Bear (Ursa Minor) and use the two stars Gamma and Beta as a pointers to Eta in Draco. TX forms part of a pentagon of stars near Eta Dra. Two useful comparison stars lie sort of North-South of TX and these are marked as K (=7.0 mag.) and N (=7.7 mag.) on the chart. At 19:11 UT I found that TX was between these two stars in brightness and my estimate was K(2)V(5)N or magnitude 7.2.

AH Draconis  is on the same chart as TX. A line drawn from Eta through the star marked P brings you neatly to AH. It sits at the tip of a collection of other brighter stars. AH looked to be pretty faint. At 19:13 AH was much fainter than star 1 (=7.0 mag.) on the chart but brighter than star 8 (=8.4 mag.). At 19:20 UT I saw that it was fainter than star 6 (=7.8) and my estimate was 6(1)V(2)8 or magnitude 8.0.

I went in for my dinner about this time and then came out to face the cold about 10pm. By then Ursa Major had risen more in the North East and I could look at the variable stars Z and RY on chart 217.02. Finding Z UMa is fairly easy. The star Flamsteed 66 forms an equilateral triangle with the two prominent stars Delta and Gamma at the "back end" of the bear and Z is close to FL66 and just south of a group of three faint stars making an unmistakable triangle. Like AH, Z was pretty faint too, if not fainter. At 22:10 UT Z was fainter than star C on the chart (=7.5) and star D (=7.9). At 22:17 I estimated that it was between stars E (=8.4) and H (=8.7) namely E(1)V(2)H giving magnitude 8.5.

Finally, on the same chart is RY UMa. If you draw a line between Gamma UMa and star B you come to a little group of stars which includes RY. At 22:14 RY was fainter than star 1 (=6.7) and star 2 (=7.4). At 22:29 my estimate was that it was between stars 4 (=7.7) and 5 (=8.3) but so close to 4 as to make no difference. So magnitude 7.7.

All text and images © Duncan Hale-Sutton 2024