Category Archives: Deep Sky Observing

NGC 908. The Snake Galaxy

Posted on by March 30, 2025
NGC 908. Slooh Australia One. Jan 8, 2025 11:24:38 utc.
Galaxy NGC 908Seeing conditions were good. No Moon.
This spiral galaxy has a bright, slightly oval nucleus. No evidence of a bar. A thick spiral arm originates from a tight “ring” around the nucleus opening to the NW. A thinner spiral arm curves from the west of the nucleus and bifurcates to the east.
The galaxy shows many bright star-forming knots. Something must have disturbed this galaxy. Even the nebulosity surround it seems ‘windblown”
This galaxy is also known as the snake galaxy. What could that snake be striking at?

NGC 1981 – The Secret Harem Revealed

Posted on by May 17, 2025

Due its proximity to very impressive neighbors, the open cluster ngc 1981 in Orion has never attracted my attention. The cluster has only 10 or so, sparsely distributed, young bright stars.

The multiple star system, Struve 750, is the northernmost star of the string of three stars, right above the Running Man.

The story goes that Aldebaran, failing to shoot one of the three zebras, was given the boot by the seven sisters. They weren’t impressed that he could not retrieve his arrow in fear of Betelgeuse who was as strong as a lion. So the arrow (which we know as Orion’s sword) is still lying there. Now I know why Betelgeuse would not allow Aldebaran to approach. He was actually guarding his own harem!

RS Ophiuchi- a rare occasion

Posted on by September 6, 2021

Life seems to be chugging along when suddenly there’s a thermonuclear eruption somewhere far far away. By far away I mean 5000ly!
What’s happening there?

A white dwarf star and a red giant are orbiting one another and maybe too close for comfort. The white dwarf siphons off material from the red giant star and developes a dense atmosphere which consists mainly of hydrogen. The newly accreted atmosphere is thermally heated by the hot white dwarf.  With this extra mass, gravity increases and the white dwarf becomes compressed which causes it to ignite.
I’ve read that only 10 recurrent novae have been identified. So what I’m following here is quite rare
To get a visual comparison, I’ve been setting up missions to RS Ophiuchi on the same telescope at Slooh and more or less at the same time of night. Cloudy weather was persistent but just as well because the Moon might have been too bright and in close proximity on those cloudy nights.
I did not give up and last night, conditions were perfect and I got a beautiful follow-up image. There’s no doubt, RS Oph is dimming and will go into slumber mode again.

To do an accurate comparison, I have not processed or cropped these images.

Gum 50 & Trumpler 23

Posted on by July 21, 2021

While working through South African astronomer, Magda Streicher’s, list of delightful asterisms to enjoy the pretty in the night sky, I have come across some very interesting deep-sky objects in the nearby regions of the sky.

I noticed a pinkish-reddish object to the north of asterism, Streicher 34. I ran the co-ordinates in Aladin Sky Atlas and identified this as Gum 50. Then another surprise! I also found the faint but destinctive open cluster, Trumpler 23 northeast of Gum 50. The cluster has an interesting shape and almost looks connected to Gum 50 by a string of stars. Could they be somehow connected?
If only I could understand what’s been written in scientific papers by Y M and Y P Georgelin and Veta Avedisova, I would have a clearer idea.

At one stage Avedisova placed Gum 50 and Trumpler 23 in the same star forming region. After measuring distances and determining spectral classes of the stars, the Georgelins cast doubt on whether the cluster was associated with Gum 50, which goes by RCW 99 as well.