Z and RY Ursae Majoris and TX and AH Draconis (1st April 2024)

A week and a half ago on the 1st April we had some more welcome clear weather. Further to that, the moon was one day to last quarter and wasn't due to rise until early in the morning. It is getting light well into the evening now and on the 1st astronomical twlight didn't end until 20:30 UT (21:30 BST). 

The constellation of Ursa Major is getting well up into the sky now and makes for a good target for variable star observing. The sky darkness around 10pm BST was good but the clarity wasn't 100%. I began, as usual, by looking at Z UMa. I now have a new pair of Hawke Endurance 10x50 binoculars to play with that I won at a competition at the BAA. I must say that I am very pleased with them. At 21:10 UT Z was fainter than star B (=7.3 mag.) on chart 217.02 from the BAA. At 21:18 I could see that its brightness was between stars C (=7.5) and D (=7.9) and my estimate at 21:21 UT was that it was midway between the two i.e. C(1)V(1)D, or magnitude 7.7.

I then moved on to RY UMa on the same chart. At 21:29 UT RY was much fainter than star 1 (=6.7). At 21:31 UT I could see it was fainter than star 2 (=7.4). At 21:35 my estimate was that it was roughly equal in brightness to star 4, that is magnitude 7.7.

The next chart I had was for two stars in Draco (chart 106.04). At 21:52 UT TX Dra was between stars K and N in brightness (magnitudes 7.0 and 7.7, respectively). At 21:54 my estimate was that TX was midway between these two stars, namely K(3)V(4)N, or magnitude 7.3. This value is on the brighter side compared to other observers at the BAA but when looking at the AAVSO data it isn't unexpected.

Finally, at 21:01 UT I saw that AH Dra was fainter than star 1 (=7.0) on the same chart but not by much. My estimate at 22:04 UT was 1(1)V(2)2 that is magnitude 7.1.

All text and images © Duncan Hale-Sutton 2024

Comet Pons-Brooks (24th March 2024).

Two weeks ago now on the 24th March, we had a break in this what seems like endless cloud, and I was able to get out and look for Comet 12P (Pons-Brooks). Although the sky was clear, conditions weren't perfect because we had a virtually full moon shining in the darkening sky. The comet was in the constellation of Pisces which was setting in the west during twlight. My first intention was actually to look for the planet Mercury and this was well-placed in the sky being at greatest elongation east on this day. It was near Eta Pisces and was quite obvious in the twilight.

I then set about looking for the comet as the sky darkened further. Not being sure about quite where it was it was difficult to pick up even in binoculars. I think I eventually located the fuzzy blob and decided to go and gather my camera and tripod to take some pictures. This was one of a number of 15s exposures I took on my Nikon D90 at ISO400:-

 

The comet is marked by a red line near the centre of the image ('click' on the image to see it at full scale). It certainly isn't that obvious. To the right of the comet in the full-scale view is the star 91 Piscium which is magnitude 5.2 and the comet is not dissimmilar in brightness to it. You can see that the field of flowering rape at the bottom is well lit by moonlight. Also seen are Jupiter and the Pleiades to the left of the image. I must admit that when I began taking more pictures I mistook the fuzzy blob more to the right of the image as the comet but this turns out to be M31! 

To see more detail of the comet I combined 19x15s such exposures, taken in the same sequence as this single image, in DeepSkyStacker and the result can be seen in the inset at the bottom right. This does show a bit more detail of the tail.

All text and images © Duncan Hale-Sutton 2024

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

Bright Aurora and STEVE on the 5th November 2023

On Guy Fawkes night at the beginning of this month we had an excellent display of the northern lights here in Norfolk and this is only the second time I have seen this phenomena in my lifetime (the other time was in Edinburgh in the early 2000's). The lights were triggered by a strong G3 geomagnetic storm caused by two Coronal Mass Ejections (CMEs) from the sun which arrived on the 4th and 5th November. As you will see from my report below I ended up being more interested in an associated phenomenon called a STEVE which was more noticeable than the aurora itself (follow the link to see more about what a STEVE is).

Here is my report that I sent to the BAA Aurora Section:-

"Having received an alert from the AuroraWatch app on my phone that the Geomagnetic activity at Sumburgh Head had reached over 600 nT at about 1700 UT I went outside to look at the sky about 18:35 UT. The sky was dark by then (Astronomical twilight ended about 18:20 UT and the Moon, at last quarter, hadn't risen). The first thing I saw was a band of milky white light quite high in the sky to the north. Being unclear whether I was seeing some sort of cloud or an aurora, I went to grab my Nikon D90 DSLR and the first picture I took was at 18:42:12 UT (see below). This showed the band of white light curving down towards the eastern horizon and passing though the constellation of Perseus. To the right of it in the picture is a patch of glowing red light.

This I took to be confirmation that this was an aurora and not a cloud formation and I have subsequently learned that the white light is called a STEVE, which is an associated phenomenon. Having only seen an aurora once before in my life, I found myself concentrating on aspects of the STEVE and perhaps neglecting the more commonly observed green dome of light due north.

 

What I thought was important about the arc of white light or STEVE was that it was a complete arch running from the eastern horizon right across the sky to the western horizon. My second picture (18:43:54 UT - see above) shows the arc passing above Polaris near the centre (but slightly to the right) of the frame. I have identified 76 Draconis as a star (at RA 20h 42m 35.0s Dec +82d 31m 52s) near Polaris which sits roughly in the middle of the arc and using software (using the date, time and my location) I have determined that this star was at an altitude of 59 deg. 44 min. So the arc most likely reached about 60 degrees in altitude due north. In my picture, the arc appears to slope further up to the right. I have confirmed that this is because in my haste my camera was not set level. I found that another star located in the arc to the right of polaris (48 Cas RA 2h 1m 57.3s Dec +70d 54m 26s) was at an altitude of 57 deg 6m.

Going back to the picture I took at 18:42:12 UT, by projecting the direction of the line of the arc towards the eastern horizon on a star map it seems that it would pass close to 47 Tauri (RA 4h 13m 56.4s Dec +9d 15m 50.0s) and at this time and location this star was at an altitude of 3 deg. 24 min. and at an azimuth of 78 deg. 46 min. measured eastwards from the north point. So it is likely that the STEVE intercepted the horizon at an azimuth of about 79 degrees (but it could be a little less than this if the arc was still curving inwards towards the north).

By 18:50:57 the white arc of the STEVE had dissipated leaving only a red glow in the eastern horizon as seen in the picture taken at this time (see above). However, after this time its strength grew again as can be seen in the images taken at 18:54:47 and at 18:56:19 (see below) and the arc was again a complete arch across the sky.

During some of the time when I the STEVE was at full strength I noticed that it appeared to be flowing from east to west along the white arc. This was evident by the fact that there were bands moving quite quickly along the arc (lines of brighter intensity with a direction perpendicular to the line of movement) and I was surprised by how fast they were moving.  I would say that they covered about 15 degrees of arc in a few seconds (so may be 7 or 8 degrees per second). 

My attention then turned to the western horizon and the picture taken at 19:00:43 shows this (see above - note that here I had increased my exposure time from 15s to 30s; see my note below about my camera settings). Although there is some evidence for cloud to the left of this picture, the white arc of the STEVE and the red glow (now to the left of it) is very much in evidence. You can also see the green glow of the aurora to the right towards the north above some television aerials. What is ineteresting to me is the symmetry of the STEVE display. What is seen in the west is a reflection of what is seen in the east and they were happening at the same time. 

By about 19:02 UT the STEVE began to dissipate again and so the part of the display I had seen lasted about 20 minutes. At 19:03:56 I took a picture towards the north (above - actually slightly east of north) at a lower elevation which shows the green and slightly red light of the aurora in that direction. At 19:08:14 the red glow in the east associated with the STEVE could still be seen. I went in for my dinner around this time but I came out again about 20:00 UT to take some more photos. Some greenish tinge low in the sky could still be seen to the north at 19:58:15 UT.

A note about camera settings. All pictures attached to this report were taken on a Nikon D90 with a Nikkor VR 18-105 f/3.5-5.6 ED lens. The settings were a focal length of 18mm, ISO3200 at f/3.5 giving a field size of 66x46 degrees approximately. Up until and including the picture taken at 18-56-19 UT the exposure time was 15s. After that it was 30s."

All text and images © Duncan Hale-Sutton 2023