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

Seven stars in one night (22nd October 2023)

A week last Sunday (the 22nd October) we had some clear weather late in the evening that allowed me to carry out a substantial bit of variable star observing. I think I am getting better at locating the stars in question and then estimating their brightness. One of the tricks of finding the targets is to be able to recognise star patterns and I have made things easier for myself by making some scribbled notes on my location charts. It is helpful to draw in lines between stars that make a shape or pattern. It becomes easier to recognise a shape when you return to it another time. Also, understanding how a chart relates to the wider constellation in which it is found is very helpful when pointing your binoculars in the right direction.

On that Sunday evening there was a bit of light cloud earlier on that was drifting over the sky. The moon was at first quarter and it was due to set at 22:40 UT. Astronomical twilight ended at approximately 18:40 UT.

I began with two variables in Draco on BAA chart 106.04. As usual I was using my 7x50 binoculars. At 22:12 UT TX Draconis (near the star Eta) was brighter than star N (=7.7 mag.). At 22:16 I determined that it was fainter than star K(=7.0) but not by much. My estimate was K(2)V(5)N which made it magnitude 7.2. This is in very good agreement with other observers from the BAA.

On the same chart we have AH Draconis. At 22:27 UT I saw that AH was fainter than star 1 (=7.0 mag.) but not by much. At 22:33 I thought it was equal in brightness to star 2 (=7.3), so my estimate was magnitude 7.3. Again this is in very good agreement with other observers.

Cygnus was still at a reasonable altitude at this time so I switched to observing CH Cygni on chart 089.04. By then most of the light cloud had dissipated. At 22:53 UT I could see that CH was much fainter than star A (=6.5 mag.) on that chart. At 22:56 I felt CH was fainter than star D (=8.0) but not by much. At 22:59 I thought it was brighter than star F (=8.5) and my estimate was D(1)V(4)F, that is magnitude 8.1. CH is an unusual variable star as I have described previously. At the moment it has faded quite a bit since it peaked in brightness between August last year and January this year (it reached about magnitude 6.5). Since June its luminosity does appear to be on the rise again.

I moved on to my next star which was pretty much overhead. This was RW Cephei on chart 312.02. At 23:16 UT RW was fainter than stars P (=6.2) and B (=6.5). At 23:18 I saw that it was brighter than star E (=7.3) but closer to B. My estimate was B(1)V(3)E or magnitude 6.7.

My fifth star to observe that night was GO Pegasi (chart 103.02). At 23:37 UT I found that GO was fainter than star B (=7.0) and brighter than E (=7.8) and my estimate was that it was mid-way between the two, i.e. B(1)V(1)E or magnitude 7.4.

My final two stars were in the constellation of the Great Bear. By midnight (1am BST!) this constellation is rising again in the north east. At 23:55 UT I saw that Z UMa is similar in brightness to star B (=7.3) on chart 217.02. At 23:57 I determined it was brighter than star D (=7.9) and at 23:59 roughly equal to star C (=7.5). So my estimate was magnitude 7.5.

Finally, on the same chart and just creeping into the 23rd October at 00:04 UT I noted that RY UMa was brighter than stars 4 (=7.7) and 5 (=8.3). At 00:06 I estimated that RY was between stars 2 (=7.4) and 1 (=6.7) but closer to 1. My estimate was 1(2)V(5)2 or magnitude 6.9.

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

All text and images © Duncan Hale-Sutton 2023

Recent observations of some variable stars

Over the last week we have had a couple of occasions when the sky has been clear enough for a while for me to get out and observe some variable stars. Last Saturday (7th October) I had just long enough to observe GO Pegasi before the murk closed in. That night the moon was 1 day past last quarter and not due to rise until 22:39 UT. Darkness is now falling earlier in the evening and astronomical twilight ended at 19:20 UT on that day. At 21:55 UT there was some hazy cloud around and some parts of the sky were obscured, however, the constellation of Pegasus was pretty clear and I was able to determine that GO was fainter than star B (=7.0 mag.) on BAA chart 103.02 but brighter than star E (=7.8 mag.). It was closer in brightness to star E and my estimate was B(3)V(5)E which made it magnitude 7.3.

This star doesn't have much of a range in magnitude variation (just 0.77 according to the BAAVSS) and, probably because of this, it doesn't appear on the list of beginner's variable stars as described by them. But then there are no beginner binocular variable stars listed in Pegasus, which seems a shame, and this is why I think I picked this one out of the BAAVSS observation program for pulsating stars. I say a shame because Pegasus is well placed at this time of year and is a prominent constellation in the sky. After a recent run of being around magnitude 7.6 it has brightened recently to 7.2 or 7.3 (near the maximum of its range of brightness) and I am glad to say that I am not the only BAA observer to have recorded this! The last time it reached this magnitude was back at the beginning of the year over 280 days ago. This seems a bit odd for a star that supposedly has a period of 79 days! However, I have found a paper by Kate Blackham (pdf) where she can't find any periodicity in this star and has declared it to be an irregular.

Two days ago on the 9th October we had another evening when there was a brief period of clear weather. Again there was quite a bit of hazy cloud and one or two more thicker patches of accumulation. The variable star TX Draconis is now heading down towards the west in the evenings but it is still at a good altitude. At 21:12 UT TX was fainter than star K (=7.0 mag.) on BAA chart 106.04 but brighter than N (=7.7 mag.). My estimate was K(5)V(2)N which made it magnitude 7.5. Another observer at the BAA on the same night estimated it to be visual magnitude 7.3, so we are in reasonable agreement. I had been intending to look at AH Draconis as well but by then a bit of cloud was obscuring my view.

I went on to look at RW Cephei which I have described before. At 21:36 RW was fainter than star P (=6.2 mag.) on chart 312.02 but brighter than star E (=7.3 mag.). My estimate put it midway in brightness between the two, namely B(1)V(1)E making it magnitude 6.9. This star hasn't changed much in brightness by my reckoning since I last looked at it on September 12th. Then I estimated to be 6.8. I think these results are in pretty good agreement with other observations from the BAA and AAVSO.

All text and images © Duncan Hale-Sutton 2023