2025 June 3

Deep Sky Update – May 2025

Callum Potter

I am finding it remarkable how bright the night sky is in the summer months at 59 degrees north. This is our third summer here and now as we are just entering June the Sun is setting in the north-north east and just dipping under the northern horizon. To all intents and purposes it’s not worth even trying any deep sky observing from here. However it is Noctilucent Cloud Season, and I have looked out on the few clear nights we have had recently, but with no luck so far.

Section Meeting 2026

My thoughts have been turning to the 2026 Annual Section Meeting, and I have allided on Saturday March 28th to be the date. This should be after the Practical Astronomy Show and the ‘Spring’ Kelling Heath star party. I said after the very enjoyable Goostrey meeting that it would be nice to hold the 2026 event in ‘the south’. So maybe you could enquire of your local society if they would be interested in hosting it, and let me know if so.

Hubble’s Variable Nebula Paper

A fascinating paper on Hubble’s Variable Nebula has been published in Monthly Notices of the RAS; “Hubble’s Variable Nebula I. Ripples on a big screen” by John Lightfoot and Aleks Scholz.
You might remember John Lightfoot gave a Zoom talk to us on Hubble’s VNe in 2021 which you can watch on the BAA video ‘jukebox’

Three Double Stars for June – Peter Morris

In the May issue I mentioned Porrima (Gamma Virginis, STF 1670) which is a binary with a period of 169.1 years which is sometimes impossible to split even in a medium-sized telescope. For my first double star for June, I offer the paradox of 70 Ophiuchi (STF 2272) which has an even shorter period of 88.4 years yet which is fairly easy to split even in a small telescope. Part of the explanation is that we are now at the widest separation and it will be more difficult to resolve in 2080. However, the main reason is that it is very close to us at only 16.6 light years, whereas Porrima is just over 38 light years distant. The current separation is 6.74 arcseconds and the position angle is 118°. The stars are magnitude 4.2 and 6.2 and are both spectral class K. They are usually observed as being both yellow or orange which is keeping with their spectral classes.

My second double Delta Serpentis (STF 1954) is a fairly tight binary in the head of Serpens (Serpens Caput). While it is clearly a binary, Gaia has given us quite different parallaxes for the two stars. The main star has a parallax of 10.8 milliarcseconds (i.e. it is 302 light years distant) whereas the secondary has a parallax of 19.0 mas (hence is 172 light years from us). It has a period of 1150 years, but with a standard error of 451 years! Yet they appear to be alone; the other two stars listed with them are both optical doubles. They are magnitude 4.2 and 5.2. The separation is 4.0 arcseconds with a position angle of 171°. They are both spectral class F stars and in keeping with this, they are both seen as yellow-white.

My final double for this month, Alya (Theta Serpentis, STF 2417) is in Serpens Cauda on the other side of Ophiuchus and borders on Aquila. The orbital period is a huge 18,000 years and hence it has a wider separation of 22.4 arcseconds. The magnitude of the stars are 4.6 and 4.9 which means they are close in brightness; the position angle is 106°. They are both hot A class stars and not surprisingly, they are both white. For reasons I cannot completely explain, Alya is one of my favourite summer doubles. The two stars are relatively bright and equal (whereas Albireo has a magnitude difference of 1.5) and they are nicely spaced while Albireo is wide. A pair of white stars may seem boring, but one can find interesting tints in the stars such as pink or green. In short, it is a subtle double in contrast to the flashiness of Albireo. There is a third star listed which is fairly bright at magnitude 6.8 with a very wide separation of 421 arcseconds and a position angle of 58°. It is an optical double.

Object of Interest – May

Markarian 478 seemed to be rather challenging, but thanks goes to Andrew Wilson and Paul Whitmarsh who both caught it with smart telescopes (Dwarf 3 and Seestar S50), and also to Robin Leadbeater who managed to take a spectrum and measured the redshift to be 0.0773 which compares well with the published figure of 0.0777 (SIMBAD).
As we have not had so many Dwarf 3 images, here’s Andy’s picture

And many thanks to Karen Smith who recently uploaded her image of LoTr 5 which although faint even with a 256 minute exposure is clearly there. Andrew Thomas tried for it using the PIRATE remote telescope, but unfortunately the exposure was rather too short to show the nebulosity, but as Andrew mentions “even a nul result is a result!”

June Object of Interest

For June Jim Latham has kindly suggested an open cluster, IC 4756, or Graff’s cluster, in Serpens. It’s a big, bright open cluster, but perhaps not too well known. It forms a very wide field pair with NGC 6633, apparently sometimes known as ‘Tweedledee and Tweedledum’.
In fact beyond the Messier and Caldwell Catalogues few clusters get much of a look in – but there are a wealth of NGC/IC targets, many of which are also in Collinder or Mellotte catalogues. It would be an interesting project to observe these, and IC 4756 would be a great start. As always, please either post your observations on your Member Album, or email to me. And sketches and visual reports are always welcome.

May Picture of the Month

There are many many excellent deep sky images in the Members Albums of May, and if you have not browsed the collection recently I would recommend that you do.
But, I picked this collection of double stars by James Weightman for many reasons, but mainly as it shows a novel use of a smart-telescope. James added a cross-hair diffraction mask to his Seestar S50 which nicely emphasises the colours of the stars.

And Finally

Although the hours of darkness are short or non-existent, I hope you might get some good observing over the coming month. Or maybe there are some summer maintenance or development projects you have in mond.
Whatever the weather, I hope you have a good summer!

Clear skies,
Callum