Recent variable star observations (23rd October, 25th and 29th November)

I have been carrying on with my variable star observations (these are mostly pulsating variables). The evening of the 23rd October was one day before last quarter and the Moon wouldn't rise until 21:11 UT. Astronomical twilight ended at about 18:40 UT. The skies were clear but the transparency wasn't great.

Here are my observations:-

TX Dra, 19:25 UT, chart 106.04, S(2)V(1)K, mag.6.9

AH Dra, 19:40 UT, chart 106.04, 2(3)V(2)6, mag. 7.6

CH Cyg, 20:08 UT, chart 089.04, A(1)V(3)W, mag. 6.7

Z Uma, 20:33 UT, chart 217.02, =C, mag.7.5

On the night of the 25th November, a month later, the Moon was 2 days past last quarter and wouldn't rise until 02:21 UT. Astronomical twilight ended at about 18:00 UT. The sky transparency was average. One of the mistakes I made was to assume that it was still British Summer Time and so I recorded my observation times as an hour earlier than they should have been. Fortunately, I saw my mistake and corrected it. Here are the observations:-

CH Cyg, 18:40 UT, chart 089.04, =A, mag. 6.5

TX Dra, 19:07 UT, chart 106.04, =N, mag. 7.7

AH Dra, 19:15 UT, chart 106.04, =6, mag. 7.8

RW Cep, 22:17 UT, chart 312.02, B(1)V(3)E, mag. 6.7

W Cep, 22:23 UT, chart 312.02, D(4)V(1)F, mag. 7.4

GO Peg, 22:50 UT, chart 103.02, B(3)V(1)E, mag. 7.6

Z Uma, 23:21 UT, chart 217.02, =B, mag. 7.3

A few nights ago on the 29th November it was 2 days before new moon. Astronomical twilight ended about 18:00 UT and the sky transparency was good. Before this observing session I was looking for some new variable stars to observe to add to my roster. The ones in Cygnus below were the first of these. I also had a go at AC Herculis which I hadn't observed since 2023.

AC Her, 19:19 UT, chart 048.4, D(1)V(1)E, mag. 7.8

AF Cyg, 21:51 UT, chart 232.02, =Q, mag. 7.6

V973 Cyg, 22:02 UT, chart 232.02, =F, mag. 6.7

All seen with 10x50 binoculars.

All text and images © Duncan Hale-Sutton 2024

Update on T Corona Borealis

Whilst I was taking pictures of Comet Tsuchinshan-Atlas on the 18th October I realised that the constellation of Corona Borealis was nicely placed for observation as well. We have been waiting about a year now for the eruption of the recurrent nova T Corona Borealis (T CrB) and, as yet, it still hasn't exploded. According to Prof. Bradley E Schaefer the star was predicted to erupt about the 25th May 2024 with an upper error bound of the 12th September. This prediction was based on T CrB entering a "super active" state in 2015 and then entering the pre eruptive "Peltier dip" in the middle of 2023. The problem with predictions is that the stars themselves are fickle and we do not have a good knowledge of exactly what is happening in the processes that lead to an eruption.

I took this image of the constellation of Corona Borealis at 18:59 UT on the 18th October. This was taken with my Nikon D90 with a Nikkor VR 18-105 lens at 75mm. The main image consists of 8x5s exposures (ISO 3200) combined in Photoshop (click on the image to see it full size). This shows the bowl shape of the crown quite well and I have marked the star epsilon CrB near to which the star T CrB can be found. The blue square in the image has been expanded upon in the top left image. This is based on 16x5s exposures at ISO3200 and the contrast has been increased in Photoshop. This inset is at the full resolution of the camera. I have used the BAAVSS chart 025.04 to label some stars and indicate how bright they are in visual magnitudes (the star is always to the right of the green label). The faintest stars being picked up are just about 10th magnitude. The position of T CrB is marked but as can be seen it is only just faintly registering and must have been 10th magnitude or fainter at the time.

Along with the rest of the BAA, I have been continuing to monitor this star as often as I can. My last observation was yesterday (the 25th November 2024) and in binoculars there was still no sign that this star had erupted. At the moment the light curve for this star is still showing that it is fluctuating between 10.0 and 10.5 magnitudes. Of course, you can now find papers that are predicting later eruption dates but who knows what will happen.

All text and images © Duncan Hale-Sutton 2024

Comet C/2023 A3 Tsuchinshan-Atlas

There has been a lot of hype about this comet in the press and, whilst it is good to bring this object to the attention of the public, over doing can mean that ordinary folks get disappointed. This was definitely not a great comet like Hale-Bopp and, although the window when you could just about see it with the naked eye was short, it has put on a reasonable display.

This long-period comet was discovered in February 2023 by ATLAS - the Asteroid Terrestrial-impact Last Alert System. After its orbit had been calculated it was noted that it had also been seen at the Purple Mountain Observatory in China, hence the dual name Tsuchinshan-Atlas. Much has been made of its 80,660 year orbital period around the sun ("your last chance to see this comet for over 80,000 years") but, in reality, four fifths of all comets are long-period, so most are "once in a lifetime".

When this comet swung into the inner solar system and became more visible to us it was a difficult morning object and seen just before sunrise. After solar conjunction the comet became an evening object in the period after October 10th. I had my first good view of it on October 18th:-

This was a single 10s exposure taken on a Nikon D90 with a Nikkor VR 18-105 f/3.5-5.6 ED lens at 18mm (ISO 800 at f/3.5). It was taken at 18:24 UT (19:24 BST) and about an hour and 20 minutes after sunset. The full moon (one day past full) was rising in the east behind me. The comet at this time was in the constellation of Serpens (Caput) and close to the border with Ophiuchus (one of the nearer stars was sigma Serpentis). This view looks sort of south west. You can see that it has a long tail streaming out behind it.

I took a number of such 10s frames and combined them together in Photoshop. Here is a cropped version of the result (16x10s, same settings as before):-

This shows the tail more clearly stretching up towards the top of the picture. I was curious to work out exactly how long the tail was and so I took this picture and made it monochrome, inverted it and increased the contrast.

In this version of the image I have marked the star 45 Herculis whose coordinates are RA 16h 47m 46s, Dec. +05 deg 14' 48''. Knowing that the comet was at position of RA 16h 08m 01s, Dec. +01 deg 52' 23'' at the time the photo was taken, we can determine the angular separation of the comet and this star. This works out to be 10.5 degrees. So the tail is longer than this and by rough measurement it is at least 12.2 degrees long.

Four days later (the 22nd October) the comet had already moved eastwards quite a bit into the constellation of Ophiuchus and I was able to see it with binoculars from my garden:-

This was a combination of 8x10s exposures at ISO3200 taken at the slightly later time of 18:44UT (same camera as before but at 48mm focal length). The image has been cropped. The bright star near the centre of the frame and just below the tail of the comet is sigma Ophiuchi. This field is 12x12 degrees and so the tail is perhaps as not as extensive as it was a few days before.

All text and images © Duncan Hale-Sutton 2024

More variable star observations (5th October 2024)

I have been trying to keep up the momentum of observing and recording variable star brightnesses. On the evening of October 5th it looked like it was going to be a good night as the sky was clear and the moon was only three days past new. However, I had to deal with intermittent cloud which meant periods of waiting until the skies cleared. Moonset was 17:58 UT and astronomical twilight ended about 19:20 UT.

I am going to start recording these observations in a more condensed form to save time. I will use a line for each star starting with the star ID then give the time of the observation in UT, the BAA chart ID, the estimate of the brightness in relation to the reference stars on the chart and the magnitude that this estimate corresponds to. These observations were all made with my 10x50 binoculars.

TX Dra, 20:57 UT, chart 106.04, K(5)V(2)N, mag. 7.5

AH Dra, 21:06 UT, chart 106.04, =2, mag. 7.3

CH Cyg, 21:47 UT, chart 089.04, A(3)V(5)W, mag. 6.8

RW Cep, 22:09 UT, chart 312.02, B(3)V(5)E, mag. 6.8

W Cep, 22:34 UT, chart 312.02, F(1)V(1)M, mag. 7.7

GO Peg, 22:53 UT, chart 103.02, B(3)V(5)E, mag. 7.3

Note that W Cephei is a new star for me to start observing. It is on the same chart as RW but previously I had not been making measurements of it. This is another pulsating variable star (semi-regular, type c) with a range in magnitudes of between 7.02 and 8.50. It has a main pulsation period of 350 days.

All text and images © Duncan Hale-Sutton 2024

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

The great solar storm of 2024 (10th May)

On the night of the 10th/11th May we had a severe G5 geomagnetic storm which caused auroras to be seen over a wide range of earth latitudes. On the night in question I had red alerts from my AuroraWatch UK app on my phone starting about 7pm BST. Initially, the strength of the alerts were from about 300 to 500 nT at Sumburgh Head but then at 10pm BST it hit about 950 nT and I knew we were possibly going to be in for a good display (compare this with the alerts we had for the aurora on the 5th November 2023). The weather was clear at this time but there was no point in looking for the aurora until near the end of twilight (the sun set about 20:40 BST and it wasn't going to get fully dark until 23:30 BST). There was a 2 day old moon but it didn't interfere with the observations as it was very low in the north west.

I went outside to have a look at the sky about 10.30pm and I could see a band of pale light over the northern horizon, so I went in to collect my camera and tripod. The first picture I took was at 22:42 BST and this clearly showed a green arc of aurora stretching across the sky, the upper parts of which crossed the constellation of Cassiopeia. From photographs I estimated that the lower part of the arc was at a maximum height of 11 degrees above the horizon whilst the upper part was at a maximum height of 28 degrees. It stretched roughly 60 degrees either side of true north.

Here is the second picture I took at 22:42:53 BST:-

You can clearly see vertical green rays in this arc and the W of Cassiopeia near the centre of the image. In all the images I took that night I used a Nikon D90 with a Nikkor VR 18-105mm f/3.5-5.6 ED lens at 18mm. All exposures were 5s at ISO 1600 at f/3.5.

I continued to take a series of images of this arc. By 22:55 BST the location and size of the arc had already changed significantly. The maximum height of the bottom and top of the arc above the horizon had changed to 17 and 35 degrees, respectively and it stretched to 70 degrees either side of due north. I also began to see some pink rays due east at about an altitude of 36 degrees. Here is a picture of the arc at 22:58:27 BST looking north west:-

The constellation of Auriga can be seen just above the trees in the centre, whilst to the left Castor and Pollux in Gemini are above the big oak tree. 

At this point in time I took a series six images about 10s apart. The rays in the arc were changing rapidly from image to image. Here is one of those images taken at 23:03:51 BST:-

You can now see that the bottom of the arc has nearly cleared the W of Cassiopeia and that the rays in the arc are well defined.

By 23:06 the top of the auroral arc had reached the zenith at its maximum and the lower part was 27 degrees above the horizon. So not only was the arc appearing to move southwards it was also swelling in extent. A few minutes later the display began to change and, unfortunately, the weather also deteriorated as well, as thin cloud began to drift in from the coast. This was perhaps the most dramatic part of the display as the auroral arc gave way to more spectacular fans of pink and red rays. This was one photographed at 23:11:25 BST:-

This view looks almost due east. To the upper right can be seen the distinctive shape of Corona Borealis. The bright star to the lower left is Vega. The colours here are very impressive ranging from red towards the lower middle of the picture to purple/pink in the upper right.

Similar patterns of pink and rays were seen in the west with the green coloration more to the north. This was the scene in this direction at 23:16:09 BST:-

Stars are just about visible but it is getting difficult to recognise constellation patterns, however, you can see the front of the "big dipper" pointing downwards at the top of this picture. Nearly four minutes later there was a nice mixture of red and green rays seen to the north:-

This was taken at 23:19:55. The front of the big dipper is again pointing downwards into the picture from the top but more to the left. The bright star halfway up the image and slightly to the right of centre is polaris. Ursa Minor extends upwards from this star. 

The aurora around this time was coming and going as gaps appeared in the ever increasing cloud. Finally, we were treated to an unusual phenomenon when rays of the aurora appear from the zenith and this is called a corona:-

It is much easier to make out the shape of the big dipper to the top right of this image (taken at 23:22:41 BST). Arcturus in Bootes is the orangey bright star to the far left. Zenith at this time is roughly where the star Mizar is located (one star from the end of the handel of the big dipper). The colour of the rays above my head at this point were strongly pink/purple. Also at this time the display was so bright that it was lighting up the garden around me.

I carried on taking pictures of bits of the display until 23:48 BST but soon after this I gave up and went to bed because of the deteriorating weather.

All text and images © Duncan Hale-Sutton 2024