RW Cephei and CH Cygni (15th January 2024)

We had another cold and clear night here over a week ago on the 15th January. The moon was waxing and three days before first quarter. It lay in the south early in the evening and wasn't due to set until 21:49 UT. Astronomical twilight ended at 18:20. 

My first target of the night was the variable RW Cephei. If you know the constellation of Cepheus, the star is relatively easy to find. The constellation was still relatively high in the sky when I went out to observe about 18:40 UT. The five stars of Cepheus Alpha, Beta, Iota, Xi and Zeta make a sort of cross in the sky and if you look at Zeta it makes a sort of triangular 'foot' with two other stars Delta and Epsilon. RW is to be found on the other side of the foot from the cross. As an aid to finding it, if you look at the binocular chart 312.02 from the BAA the stars P and B and another star of similar brightness make a sort of parallelogram with RW.

At 18:44 UT with 7x50 binoculars I could see that RW was fainter than P (=6.2 mag.). At 18:48 I judged it to be brighter than B (=6.5) but only just. At 18:49 I thought it was much brighter than E (=7.3). Therefore my estimates at 18:48 was P(2)V(1)B i.e. magnitude 6.4.

This is all a bit curious because it seems, relative to other observers at the BAA, I am a bit bright in my estimate yet I am sure that this is what I saw. For example, another observer estimated the brightness to be 7.0 at 18:45 UT on the same day! So we are 0.6 magnitudes apart! Their estimate makes RW 0.3 magnitudes brighter than E and 0.5 magnitudes fainter than B. This seems very at odds with what I recorded. One of the other things I think is strange is that I was very much more aware of the colour of RW (which was red) whereas usually for these stars the colour isn't very obvious at these magnitudes. Hey, ho. I will stick by what I saw.

I moved on to look at the variable CH Cygni in the wing of Cygnus the Swan. This constellation was flying down towards the west and would be difficult to observe in a couple of hours. At 18:58 UT CH was much fainter than star A (=6.5) on chart 089.04 from the BAA and star W (=7.3). At 19:03 I thought it was brighter than star D (=8.0). My estimate at 19:06 was that CH was near to being midway between W and D but slightly nearer to W, that is W(3)V(4)D which is magnitude 7.6.

I am pleased to say that there is no disagreement with this observation and those from other BAA observers on this date!

All text and images © Duncan Hale-Sutton 2024

Perseus and the Pleiades with a Sony RX100

A friend of mine asked me to try taking some pictures of the night sky with my Sony RX100 as he was thinking of purchasing the camera himself. On the 9th January when I was also making some variable star observations I took this image of the sky with this camera:-

My settings were as follows: aperture f/1.8, shutter speed 15s, 35mm equivalent focal length 28mm, ISO 1600, white balance auto, manual exposure and colour space Adobe RGB. The main features are the constellation of Perseus (upper centre) and the Pleiades star cluster (lower right). Also the constellation of Auriga is poking into the picture at the bottom (centre left).

I don't think the camera has done too badly. I had to rely on autofocus as I hadn't looked up how to do it manually, but I think it is possible. The star images are a bit distorted into triangle shapes as you go to the edges of the frame but at f/1.8 this is probably to be expected. I reckon you can see stars down to about 9th magnitude. I have also marked a few other objects (mostly star clusters - click on the image to get a better view) that can be seen but it is good to see the galaxy M33 appear near the edge of the frame at the top right. I think the California Nebula was probably a bit of wishful thinking but I thought I could see a bit of red colouration.

All text and images © Duncan Hale-Sutton 2024

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

T Coronae Borealis on the morning of the 26th December 2023

T CrB is a recurrent nova that is currently of interest because it is likely to go nova sometime soon. The last two eruptions were in 1866 and 1946 (a separation of 80 years) and the current prediction for the next one is 2024.4+/-0.3. It could reach magnitude 2 which would mean it would be roughly as bright as alpha CrB.

The BAA have 3 useful charts to use when locating T. These are a wide 50 degree field, a 9 degree field for use with binoculars and an inverted 2 degree field to be used with a telescope. The chart number is 025.04. T is located near Epsilon CrB. This star (labelled A on the 9 degree chart) forms a roughly equilateral triangle with the stars labelled E and F. T is to the west side of the line between A and F and a roughly halfway between them. There is a small group of three stars to the east of this line which point towards it.

At the moment (5th January 2024) T is about 10th magnitude. Members of the BAA variable star section have obviously been asked to keep an eye on this star but currently the constellation of Corona Borealis is only visible in the morning before sunrise.

On Boxing Day morning just passed (the 26th December) I happened to be awake around 6am and so I thought I would check to see if the nova had appeared. The sky was clear but the moon (1 day before full) was still in the sky in the west and astronomical twilight began at 06:00 UT. Nothing was obvious to the naked eye around that time. With 7x50 binoculars I searched for the location of T without seeing anything. The faintest star I could see in the area (at 06:32 UT) was the star labelled P which was magnitude 8.4. So T was fainter than this at this time. The last confirmed visual observation of this star was around the 1st December but there have been some CCD determinations. So I must try and get up early one morning soon and have a go with the telescope.

All text and images © Duncan Hale-Sutton 2024