Six variable star estimates (11th September 2024)

About two weeks ago, on the night of the 11th September, we had some very good clear skies and the first quarter moon had set by 21:23 UT. We are moving into autumn now and it gets properly dark by 20:30 UT. The transparency of the sky was shown later on in the night when looking at the variable Z UMa but I will come to that shortly.

I began with a couple of stars in Draco. Using my 10x50 binoculars and BAA chart 106.04, at 21:50 UT I could see that TX Dra was fainter than star K (magnitude 7.0) but marginally brighter than star N (mag. 7.7). My estimate was K(5)V(2)N or magnitude 7.5.

On the same chart is AH Dra. At 22:00 UT I could see that AH was fainter that star 1 (mag. 7.0) but brighter than star 2 (mag. 7.8). At 22:09 UT my estimate was that is was roughly equal in brightness to star 2, that is magnitude 7.3.

The constellation of Cygnus is still high in the sky at this time and so I next looked at the star CH Cygni on chart 089.04. At 22:24 UT CH was fainter than star A (mag. 6.5) but brighter than star W (mag. 7.3). At 22:30 UT my estimate was A(3)V(5)W or magnitude 6.8.

The constellation of Cepheus, by contrast, was directly overhead. Using chart 312.02 at 22:47 UT I saw that the variable RW Cep was fainter than star B (mag. 6.5) but brighter than star E (mag. 7.3). At 22:50 UT my estimate was that it was midway between these two stars in brightness, that is B(1)V(1)E, i.e. magnitude 6.9.

Now onto a couple of stars in Ursa Major. This constellation hangs quite low in the sky in September at midnight BST. It almost "stands" on the northern horizon. I had been thinking because of its low altitude that it might be difficult to view the variable stars I had in mind due to absorption in the atmosphere but it was a testament to the clarity of the sky that this wasn't the case.

Firstly, I had a look at Z UMa on chart 217.02. This star was very faint but just visible. At 23:05 UT Z was fainter than stars H (mag. 8.7) and L (mag. 8.9)!! Now I couldn't see star M (mag. 9.5) but I reckoned that Z was only a couple of tenths fainter than L. So my estimate was L-2, i.e. magnitude 9.1. This must be one of the faintest observations of this star I have ever recorded.

On the same chart is the variable RY UMa. At 23:18 UT RY was fainter than star 1 (mag. 6.7) but brighter than star 2 (mag. 7.4). At 23:23 UT I thought that RY was closer in brightness to 2 rather than 1 so my estimate was 1(5)V(2)2, i.e. magnitude 7.2.

All my estimates are in good agreement with other observers from the BAA.

All text and images © Duncan Hale-Sutton 2024

Noctilucent cloud activity in June 2024

Earlier in June I saw a couple of displays of noctilucent clouds (look at this previous post to find out what these clouds are and how they are formed). The first was on the night of 23rd/24th June when we were in Suffolk near Bawdsey and I initially saw them at 21:51 UT:-

I estimated that they reached a maximum elevation of about 18 degrees above the horizon and stretched from about azimuth 300 to azimuth 10 (azimuth 0 points due north and then increases eastwards along the horizon - so due east is 90 degrees, south 180 and west is 270). They were mostly in the form of bands (type 2) and waves (type 3).

I carried on seeing them for about 25 minutes (until 22:15 UT):-

By then the clouds had sunk lower to the horizon (just a maximum elevation of 12 degrees) and they stretched from azimuth 313 to 357 degrees. Both pictures were taken on a Samsung SM-A217F camera phone with an exposure of 1/10s, f/2.0, ISO 2000.

Five days later on the night of the 28th/29th June I observed another display from my home in Neatishead. Again, I caught sight of them at a starting time very similar to before (21:52 UT):-

You can see the NLC's as white wavy bands (type 3) behind the chimney pot of the house next door. Some foreground normal cloud is obscuring the view. I reckoned that the maximum elevation of the clouds stayed pretty much constant at 18 degrees above the horizon.

Eight minutes later at 22:00 UT the clouds appear brighter as the sky darkened:-

There appeared to be some brighter knots in the wavy clouds. At 22:12 UT the clouds appeared very bright and the structure was more complex:-

Also the clouds didn't appear to extend so far eastwards (although part of this may be due to obscuring foreground cloud). At 22:28 UT the clouds began to fade and I stopped observing:-

The camera and exposure settings were the same as above.

All text and images © Duncan Hale-Sutton 2024