Tightly bound spherical collections of stars known as “globular clusters” exist in most galaxies, orbiting around their cores. Our own Milky Way galaxy has about 150 or so. Most astronomy enthusiasts who live in the Northern Hemisphere are quite familiar with the “Great Hercules Cluster” M13 located in the constellation Hercules. An impressive sight in any telescope, the Hercules cluster has a few hundred thousand stars and measures 145 light years in diameter. It is faintly visible to the naked eye. M13 is by far the largest globular cluster visible from the Northern Hemisphere, but it isn’t the largest in our galaxy. That title belongs to Omega Centauri, or NGC 5139, in the constellation Centaurus. Unfortunately Omega Centauri is visible “mainly” from the Southern Hemisphere. The reason I say “mainly” is that last year I accidentally came across it while casually sweeping the southern horizon with a pair of binoculars from the deck of the house up at Orion’s Belt Observatory! It turns out we actually do have a small 2 hour window of visibility from this location. Omega Centauri is quite visible with the naked eye from a dark site and looks to be about the same diameter as the full Moon! By contrast to M13, Omega has several million stars packed so densely they are on average only 0.1 light years apart from each other! At 180 light year diameter it is only slightly larger than M13 but has many times the number of stars.
While working on the “pier 2” equipment, I decided to take a couple of test images of the cluster during the brief window of visibility just to see what I could see! Of course this is not an easy target from this location, with a maximum elevation of 7-8 degrees above the horizon! The observatory has panels on the south wall that can be dropped down to access the horizon. This is exactly the situation they were designed for! I pointed the Tak 180 to Omega and tried a few 3 minute exposures. The results were much better than anticipated. The dark skies certainly help. On the screen was the glorious Omega Centauri cluster! The image I thought was pretty clean and stars well resolved for just a single exposure. The Tak 180 is a known bear to collimate and I did the best I could just for this test but it will need some work..a subject for a future post. Anyway I felt this was going to be a definite legitimate target in the future based on this preliminary test!
Thanks for reading!