Z and RY Ursae Majoris and TX and AH Draconis 27th March 2023

It has been a while but at the end of March we had a clear evening when I could get back to do some variable star observing. I haven't looked at these stars since the end of last year and so I was keen to get some new estimates. Unfortunately, the moon was in the sky and it was 2 days before first quarter. Also, the evenings are getting lighter and astronomical twilight didn't end until about 20:20 UT (21:20 BST).

I began with my current favourite Z UMa. Using chart 217.02 from the BAA and my Nikon 7x50 binoculars, I was able to see star H on the chart near to Z and this was a good sign as it meant my limiting magnitude was fainter than H which is 8.7. I could see that Z was brighter than star D (=7.9) and C(=7.5) and at 20:19 UT I estimated that Z was between stars A (=6.3) and B (=7.3). I found that Z was 2 points from A and 1 point from B, namely A(2)V(1)B which made it magnitude 7.0 (to 1d.p.). This is in good agreement with estimates from other BAA observers.

So this indicates that this star is approaching its peak luminosity. I have written a thread about this star on the BAA Forum. What makes this star interesting at the moment is that the recent rises in luminosity have been double peaked and it may be this is due to the two pulsation periods that contribute to the brightness changes of this star. In my latest post I considered whether this was a reasonable explanation.

Using the same chart I then went on to look at RY. I saw that this variable was fainter than comparison star 1 (=6.7). In fact, I thought it was roughly equal in brightness at 20:33 UT to star 2 which is magnitude 7.4. Other observers in the BAA had this star at magnitude 7.6 and 7.7 on this night, so perhaps I was slightly on the bright side with my recording.

I then went onto chart 106.4 to have a look at TX Draconis. This star was lower in the sky than the previous two and rising in the East. At 21:34 UT TX was fainter than star K (=7.0) but marginally brighter than star N (=7.7). I estimated it to be 3 points from K and 1 from N, that is K(3)V(1)N. This made magnitude 7.5 (to 1d.p.). I think this estimate was fine.

Finally, from the same chart I had a look at another semi-regular variable AH Dra. At 21:44 I noted that this star was fainter than star 1 (=7.0) on the chart. At 21:49 I thought it was between star 2 (=7.3) and star 6 (=7.8) in brightness, namely 2(1)V(1)6, which made it magnitude 7.6 (to 1 d.p.). Other observations of this star are a bit sparse at the moment so I am not sure if I was on the ball with this one.

All text and images © Duncan Hale-Sutton 2023

M42 and the Running Man Nebula

On the same evening that I was taking more pictures of the comet C/2022 E3 I decided to have a quick look at M42 in Orion as it was nicely placed. As I was using my Celestron 102SLT I wanted to do the wide shot which included the Running Man Nebula which lies to the north of M42. I thought I had captured this image since I came down to Norfolk but it seems that I haven't and the last time I attempted this was in 2006 when I was using a 200mm lens in Yorkshire. This time I managed 20x30s at ISO3200 and then I combined them in DeepSkyStacker using auto adaptive weighted average, binned the final image x2 and modified it using levels in Photoshop. This was the result (you can click on any of the images to see an enlarged version):-

I was pleased with the result. The stars have come out quite sharp and there is plenty of detail in the nebulae. M42 is the pink fan shaped nebula to the right with its four bright stars of the Trapezium in its centre. Below and very close to M42 is another nebula designated by Messier and this is M43. It is seen as an almost circular nebula, with a central star, cut off from M42 by a dark lane of dust and gas. The Running Man Nebula, as it is called, is to the left of the image and appears as a faint blueish nebula with dark lanes running through it. I have reproduced a larger version of it here where I have labelled the contributing parts to it:-

With this orientation the dark lanes that lie in this reflection nebula do really look like a man with his legs splayed as if running.

To compare these images with my previous attempts here is an image that I took from 2006 with a 200mm focal length lens:-

All text and images © Duncan Hale-Sutton 2023

Comet C/2022 E3 (ZTF) begins to fade

Last Wednesday evening (8th February 2023) we had some more clear weather before the waning gibbous Moon rose at 19:58 UT. The seasons are moving on now and astronomical twilight lasts until nearly 19:00 UT. Comet C/2022 E3 is now beginning to fade and is moving fast across the sky. On the 8th it was in the constellation of Auriga not far from iota Aurigae and the border with Perseus and Taurus. COBS indicates that it was about 6th magnitude. I again set up my Celestron 102SLT on the HEQ-5 mount but I found setting up was more complicated this time because I lost power to the drive momentarily whilst doing the sky alignment. Anyway, I managed 26x30s frames of the comet (ISO 3200) before I accidentally nudged the tripod. Here is one such frame taken at 19:00 UT (binned x2 and modified in Photoshop using levels):-

I then combined all 26 frames in DeepSkyStacker (comet stacking, star trails, auto adaptive weighted average). The resulting frame was then modified in Photoshop using curves and levels, binned x2 and then cropped slightly. This was the result:-

The green colour of the comet's coma is nicely seen. The dust tail is obvious but the ion tail was too faint to be seen here. The first frame was taken at 18:51 UT and the last at 19:09. I think the flattening of the image to remove vignetting of the telescope went slightly better this time as I took some flats about sunset. Basically these are out of focus shots of clear patches of blue sky.

All text and images © Duncan Hale-Sutton 2023

Further pictures of Comet C/2022 E3 (ZTF)

Just over a week ago on a Sunday evening (the 29th January) we had some good clear weather but with a (one day past) first quarter moon to contend with. At this time Comet C/2022 E3 was approaching its nearest distance to us and its brightest magnitude (about magnitude 4.5). Since then it has begun to fade and its distance from us is increasing.

I decided to set up my Celestron NexStar 102 SLT on my borrowed HEQ-5 mount to observe it. The setting up all went much better than on previous occasions and I successfully managed to align the polar scope on the pole (it is an equatorial mount). Part of my decision to do this was to see if I could extend exposure times beyond 30s but more of that later. The NexStar has a reasonably wide field of view which makes it ideal to capture the tail of the comet. I began by taking 30s frames of the comet with my D90 camera attached at the prime focus. Here is one such frame:-

I was pleased by how sharp the stars are in this image. The comet at this time was in the constellation of Camelopardalis and just over the border from Draco. It was at a very high declination of nearly +80 degrees and so not far from the pole. This image is about 2.05x1.37 degrees. North is towards the top left-hand corner and East to the top right-hand. It was surprising how fast the comet is moving across the sky during the 13 minutes I was observing it.

 

 

The above picture is combination of the first and last frames that I took over this period. The first was taken at 21:28 UT and the last at 21:41. The comet has moved by about 55 pixels during this time and, at approximately 3.44 arc seconds per pixel, this corresponds to 3.2 arc minutes. So it was moving at 0.24 arc minutes per minute or 14.6 arc minutes per hour.

In all I took 19x30s frames (just short of ten minutes, ISO 1600) and combined them in DeepSkyStacker:-

The background stars have disappeared because I have centred the stacking process on the comet and used the median rather than the average. This has helped bring out details in the tail. All the images I have shown are binned x2 and have been modified in Photoshop to bring out the fainter detail. In this image above it is possible to see two tails. The dust tail causes the wedge of brightness that emanates from the comet at the 7 o'clock position. The ion tail can be seen as a thin line that emanates from the comet nucleus at the 3 o'clock position. Closer inspection (click on the image) reveals that this ion tail extends right to the edge of the frame and splits into three parts.

Finally, I did try to get more photographs of the comet a few days later on the 31st January using the same setup. This time I extended the exposure time to a minute with the use of a digital remote control for the camera. This worked well enough but by then the moon was waxing gibbous and the faint detail from the comet was missing. This is a one minute exposure (ISO 800) I took at 20:14 UT:-

The comet was still in the constellation of Camelopardalis at this time having crossed a bit of Draco again.

All text and images © Duncan Hale-Sutton 2023

Photograph of Comet C/2022 E3 (ZTF)

Saturday night (the 21st January), after attending a BAA meeting in London, we had some clear but cold weather in the evening. Comet C/2022 E3 had by this date moved further north and just crossed over the border of the constellation of Bootes into Draco. It is now becoming easier to see before midnight and hangs in the sky below the north celestial pole. I took this picture just after 11pm GMT:-

I used my Nikon D90 to take 24 exposures of 10 seconds each. The lens was set at 105mm and the ISO at 6400. The exposures were combined in DeepSkyStacker and the resulting frame was stretched using curves in Photoshop, binned x2 and then cropped. Barrel-distortion and vignetting were removed by using PTLens. The field seen here is approximately 9x6 degrees. North is towards the top left-hand corner of the frame, East towards the top right-hand corner. The first frame was taken at 23:02 and the last at 23:08 UT.

The comet can be seen as a greenish smudge in the lower part of the frame. The tail extends in a north-easterly direction. There are some 6th magnitude stars nearby and the comet doesn't seem to be brighter than these.

All text and images © Duncan Hale-Sutton 2023

Comet C/2022 E3 (ZTF)

We have another brightish comet gracing our skies at the moment and this is C/2022 E3 (ZTF). The Comet is currently in the constellation of Bootes and heading north towards Draco (see the graphic by Pete Lawrence in this article by the Sky at Night magazine). It is currently about 6th magnitude and so it is approaching naked eye visibility.

On Sunday morning (the 15th January) I had woken up early and not been able to get back to sleep, so I went to see if I could find this comet. We had clear skies and it wasn't difficult to locate using 7x50 binoculars as it was roughly halfway between the stars Beta Boo and Eta Her. Not wanting to go outside and endure the sub-zero temperatures, I decided to try and make a drawing of what I could see but I had to lie on the floor to get a decent view. This is what I saw:-

The stars 2, 4 and Chi are part of Hercules and Nu 1, Nu 2 and Phi are part of Bootes. The comet is the smudge near the centre of the field. I started the observation at 4:34 UT and finished at 5:22 UT. There was a last quarter moon shining in the south and so the sky wasn't that dark. I compared the comet to M13 (a globular star cluster in Hercules) which is visual magnitude 5.8 and I thought it was fainter than this but perhaps twice the area. The comet was estimated to be magnitude 6.5 at the time.

All text and images © Duncan Hale-Sutton 2023

GO Pegasi 9th January 2023 - part 2

The other variable star that I had a look at a week ago was GO Pegasi. I haven't observed this star before and it is conveniently located roughly halfway between alpha and lambda Pegasi at the right-hand side of the square of Pegasus. The BAA chart 103.02 places GO near the star Flamsteed 51. According to the BAAVSS this is another semi-regular variable (SRb) with a main period of about 79 days and a range in luminosity of between 7.14 and 7.91 magnitudes (so not very large).

At 18:50 UT I saw that GO was fainter than star B (=7.0 mag.) on the chart and at 18:57 I estimated that it was marginally brighter than star E (=7.8). So my estimate was B(3)V(1)E which made it magnitude 7.6.

I think this is in pretty good agreement with observations from the BAAVSS and the AAVSO.

All text and images © Duncan Hale-Sutton 2023