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

RW Cephei 9th January 2023

On Monday, in the early evening, we had some clear dark skies before the moon came up and so I was able to make a couple of variable star observations. The moon was 3 days past full and wasn't due to rise until 18:32 UT. Twilight ended at 18:10.

I started off with another observation of RW Cephei. The constellation of Cepheus at this time is still relatively high in the sky. At 18:24 UT I noted that RW was fainter than star E (=7.3 mag.) on BAA chart 312.02 but not by much. At 18:27 I confirmed that RW was brighter than star H (=7.8 mag.) and so my estimate was it was 1 "point" from E and two "points from H (or E(1)V(2)H). This made it magnitude 7.5 to 1 d.p.

This means that, in my estimation, the star hasn't shifted in brightness since Christmas Eve 16 days ago. However, my estimate seems slightly at odds with what other members of the BAA are seeing.

The above light curve courtesy of the BAAVSS shows all the data between the 01/01/2022 and the 09/01/2023. The last data point to the extreme right is the observation I have made here. It seems my magnitude 7.5 values are probably 0.2 magnitudes from the mean and on the upper edge of the spread of values. I find it hard to understand how the estimates could be as faint as magnitude 7.9 as this would mean that it was fainter than star H which I am pretty sure it wasn't.

Here is the light curve for this star from the AAVSO:-

What is interesting here is that AAVSO shows a similar spread in values between about 7.4 and 8.0 magnitudes but curiously CCD measurements (shown in green squares) can't quite agree either even though these should be much more accurate than visual observations. Note that there is a marked increase in the number of observations around JD 2459929 (16 December 2022) as this was when an alert from the AAVSO went out asking for more data. Prior to this date one observer (VOL) had a nice sequence of DSLR observations (in green squares) with very little scatter. Here is his data shown on its own:-

This observer seems to be seeing what I see in that dimming of RW is flattening out and tending to magnitude 7.5 (however, there may be a 0.2 magnitude systematic difference between visual and DSLR observers).

All text and images © Duncan Hale-Sutton 2023 except those by the BAAVSS and AAVSO.

Mobile phone picture of the Moon

Later on Monday evening (the 2nd January) I thought I would have a go at photographing the moon using my mobile camera (a Samsung Galaxy A21s) and my Orion OMC-140 Maksutov-Cassegrain. I have heard that it is possible to get quite good pictures by holding the camera lens up to the eyepiece of a telescope and taking a picture 'afocally'. The difficulty in doing this by hand is getting the telescopes image of the moon lined up with the camera of the phone and then holding it steady enough so that a picture can be taken. However, after some experimentation I did get one shot that I thought was pretty good:-

Here I used a Celestron 25mm eyepiece and the camera settings were 1/50s at f/2, ISO40. This was how I saw the image in the eyepiece. I was using a star diagonal, so even though North is at the top East is to the right and West to the left (which is the opposite way to which we usually see the moon with the naked eye). I was really impressed with the results and may try and do more work with my phone camera, perhaps purchasing a holder that can attach to the eyepiece to keep everything steady. If you 'click' on the image you can get an enlarged view which will show more of the detail of the 'seas', mountain ranges and, of course, craters.

All text and images © Duncan Hale-Sutton 2023

A low apparition of Venus on the 2nd January 2023

On Monday this week we had some nice clear conditions in the late afternoon and so I thought I would go out and see if I could find Venus and Mercury. In fact, it would have been virtually impossible to see Mercury as it was lost in the glare of the setting sun. You can use the BAA computing section's applet to find the position of the planets (and other objects) at any time. I did find Venus and so I got this image at 16:39 UT:-

This was about 34 minutes after sunset and Venus was about 4.4 degrees above the horizon (at this time Mercury was just 2.2 degrees above that level). This is looking almost SW. At the present time Venus is emerging from conjunction with the sun and will reach its greatest elongation east on June 4th. Its apparent diameter is quite a small 10.4 arc seconds and the phase is about 96%.

All text and images © Duncan Hale-Sutton 2023