2025 May 5

Deep Sky Update – April 2025

Callum Potter

A little delay in posting this month’s update. I have been away giving a talk on beginning deep sky observing to Sigma, the astronomy society of Moray based in Elgin. A super society, and great to meet up with old friends, meet some BAA member,s and make new acquaintances.

In Orkney I am always amazed at how quickly the nights draw out after the equinox – already true dark sky (astronomical darkness) is just a short period overnight. So chances for deep sky observing are becoming limited. I will need to start using up some of my accumulation of iTelescope points instead. 

Astrophotography in Chile – Martin Griffiths

Chile is an incredible country with some of the most diverse scenery in the world.

From the Pacific coast to the high Andes Mountains, from the Altiplano and the Atacama desert to the vineyard filled valleys that give some of the world’s best wines, there is something for everyone. But that is just daytime; at night, the world’s darkest skies fill the dry and tranquil air above the desert and mountains and renders Chile an astrophotographer’s dream. The southern Milky Way, Eta Carina, Omega Centauri, Centaurus A and the Sagittarius star clouds high above with the sting of the Scorpion and many more are there to be captured.

The southern skies are a delight to behold, especially to those from northern latitudes. Chile extends from 35 degrees to 71 degrees south and experiences the driest climate in the world. Usually it basks in 320 days of glorious sunshine and is a Mecca for the world’s largest observatories such as the VLA at Cerro Paranal, The ESO’s La Silla and Las Campanas observatories, Cerro Tololo and of course the Vera Rubin Telescope and Gemini South. For those of us with more modest equipment, smaller observatories that cater for the amateur are readily available such as IoCrux at San Pedro de Atacama, El Pangue and Omega Astronomy Centre in the El Qui Valley and many others that give clear skies, excellent advice and highly trained volunteers who know the sky and telescopes well. If one takes in a guided tour, then several of the large observatories may be open to the public.

Astrophotographers rely on their own equipment and driven mounts which can be taken as hand luggage if they do not exceed the airline’s guidelines on weight. The clarity of the air, the lack of light pollution in most centres and the absence of haze make Chile an exciting prospect for those wishing to see and photograph the southern sky.

There are several excellent local photographers who can give talks, showcase their work and hand on their experiences to novices and experts alike. Ones such as Alexis Jaldin love to promote the country as a centre for astrophotographers and guides such as Rodrigo Sebastián Ruiz Mardones and Pablo Ignacio Sandoval Aranda in Santiago can arrange visits and astrophotography sessions, whilst in the El Qui Valley outside the city of La Serena, Jorge Retamales is an experienced astronomer and guide at La Silla and Pangue observatory. Each one of them does all they can to make your visit exceptional.

I have included some photographs I took on my trip in March/April 2025. Portable telescopes such as Dwarf or Seestar make the most of the wonderful clarity of the night skies. Exposures on my Canon 6D with a 14mm lens were no more than 30 seconds.

I hope that I have whetted your appetite for the potential of Chile and its dark skies. If you wish to contact any of the guides and arrange a visit to this beautiful country then please use the contacts below.

Rodrigo Sebastián Ruiz Mardones: rodrigo@farouttrails.com info@farouttrails.com

Jorge Retamales: cieloabierto62@gmail.com

Alexis Jaldin: https://www.facebook.com/p/Alexis-Jaldin-Astrofotograf%C3%ADa-y-Fotograf%C3%ADa-100063952518755/

Here are some some of Martin’s photos.

Three Double Stars for May – Peter Morris (Double Star Advisor)

Porrima (Gamma Virginis, STF 1670) is now a relatively easy double star having been unresolvable even in medium-sized telescopes as recently as 2007. The separation is now 3.47 arcseconds and the position angle is 352°. The stars are both magnitude 3.5 and are both spectral class F. They are usually observed as being white although they could be seen as yellow-white, given their spectral type.

May is an excellent time to observe doubles in the constellation of Boötes. The best-known is Izar (Epsilon Boötis, STF 1877), which was called “Pulcherrima” (the most beautiful) by the veteran double-star astronomer Wilhelm Struve. Its duplicity was discovered by Willian Herschel in September 1779. It is a rather tight double with a separation of 2.9 arcseconds and the position angle is 346.6°. The differences between the magnitudes of the two stars (2.6 and 4.8) make it more difficult to resolve, but it should be a straightforward split in a 4-inch telescope. It is thought to be a binary star, but this is still unconfirmed. The beauty comes from its colours. The main star is a K type and the companion an A type which should make it a fairly typical yellow and blue pair. Smyth called then pale orange and sea-green and Struve said they were gold and blue. More recently Sissy Haas has described them as amber-yellow and deep blue. Personally I see them as orange and green.

Alkalurops (Mu Boötis) is another great double in Bootes. It consists of a very wide double and a very close pair, which makes for a nice contrast. The wide pair (STFA 28) is 109.2 arcseconds and a position angle of 171°. Their magnitudes are 4.3 and 7.1. Despite the wide separation, it is a binary system. The secondary (STF 1938, Ba and Bb) is a binary with an orbital period of 256.5 years. At its narrowest separation (around 2120), it will impossible to split in a small telescope, but this will not happen in our lifetime. Now it is narrowing slightly, but it is very slow. The current separation is 2.18 arcseconds, but as the two stars are similar magnitudes (7.1 and 7.6), the split is not too onerous at a high magnification. The main star is spectral type F, the brighter of the two companions is spectral type G and the spectral type of the third star is not known. The main star is usually seen as yellow-white or yellow (although white has been reported) and the close pair are seen as both yellow (sometimes with a reddish hue) or yellow and orange. I see them as yellow, yellow and orange.

PV Ceph and Mr. G. 

There has been some excitement over the developments in this variable nebula. And it was nice to see a few people image the recent changes. It would also be nice if observers could add the available VNe to their observing programmes, so we can have some continuous record. Richard Sargent (VNe Coordinator) collects images for the archive, and FITS images would be particularly appreciated so that comparative analysis can be done. 

April Object of Interest – LoTr 5

LoTr 5 proved rather a challenging target – I think I just about got it with my Seestar S50. And many thanks to Iain Cartwright, Jonathon Elliot, Mark Fairfax, Paul Whitmarsh and Manolo Rodriguez who all had a go at it. Jonathon pushed his processing to get a result but later revealed there was a filter mix-up so what was supposed to be OIII was in fact SII. In my Seestar image the background was not very smooth, which I put down to noise and poor processing, but it’s interesting to see it is present in the other images too so perhaps there is some IFN or other structure there.  Here is Manolol’s image:

Object of Interest for May

For something a bit different this month the quasar Markarian 478 (Mrk 478) in Bootes is the target which is nicely placed. It is about magnitude15, and about 1 billion ly distant.  It’s ‘hosted’ by the galaxy PGC 52510 which, according to Bob King’s 2019 Sky & Telescope article is visible with a 15″ scope. It’d be interesting to see what can be imaged. We couldn’t find any pictures on-line, so possibly a nice challenge there.  Jim had a look with his 14″ recently under clear but slightly hazy skies and could only see a faint stellar object at high power. Possibly something of the extended galaxy would be visible with better conditions

April Picture of the Month

Steve Knight has been in La Palma with his Seestar S50 and captured the splendid globular cluster Omega Centauri, one of my favourite targets.

And Finally

Although the hours of darkness are getting ever shorter I hope you will take advantage if you get the chance to do some observing of the summer targets that are coming into view.

Clear, dark skies,

Callum