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!
Screen shot from the “Stellarium” program showing the location currently of Omega Centauri (broken square icon due South) at its maximum elevation during transit of a wopping 7 degrees above the horizon! Some of the brighter stars in the constellation Centaurus are seen to the left
NGC 5139 or Omega Centauri is the largest globular cluster in our galaxy! This is a single raw image taken from Orion’s Belt Remote Observatory using a Tak 180ED on a Paramount MX+. 3 minute exposure. Canon 60Da camera. I did a quick collimation with CCD inspector and it’s actually pretty decent but if you look to the left side of the image the stars are a little elongated. I was quite thrilled with this quick test and can certainly add the cluster to the list of obtainable targets from this location!
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Now with the eclipse excitement settling down it’s time to return to the night time world! Back at Orion’s Belt for the holiday weekend we have arrived at a critical point in the installation process for the newly acquired 16″ telescope. Time for optical testing which means we have to take an image! I guess technically it’s sort of a first light but I don’t really count it as such because it’s just star testing. However it is kind of a big deal because if we take this image and the stars are totally jacked up either we have to start collimation from scratch which means we have to buy more collimating equipment or in the worst case scenario there is an optical problem which needs repair! After all the scope is shipped from overseas. Who knows what could have happened. There is also the issue of focus, if it can be reached at a point somewhere in the middle of the focuser travel so we can do automated focusing. There are no “spacers” with this system. We had to get the right adaptor with just the right amount of backfocus. Hopefully we did the math right!
To get to this point it took the last 2 months slogging through the installation of the accessory equipment on the scope: the focuser, control system etc. You can see the blow by blow narrative in this page. I think overall it really went fine. Yes there were some issues but with this kind of stuff how can there not be? Mostly I was very anxious and apprehensive due to the huge expense of this equipment, every step of the way worrying about something breaking or malfunctioning. But thankfully no disasters yet and I got through it and learned a bunch in the process!
All the operating components are now in position. ‘A’ is the USB hub. ‘B’ is the focuser. ‘C’ is the camera. The OS bus controller is on the other side of the scope. Cables are secured to the holes in the telescope frame with the use of cable ties.
Looks more like a NASA space probe than a telescope, but then again we are able to “travel” to the far reaches of the Universe with it!
So now the first ever image taken with the RiDK 16″:
First ever image taken with new set up!
What we see are defocused star images but still pretty round all the way from side to side. Yay! We probably don’t have to send it back! The 2 lines in the image are called “column defects” and are present in the ccd sensor. These do occur with the standard “class 2” ccd sensors (class 1 sensors with no defects are generally used for research). The column defects do process out pretty easily with dark frames
Near focus is reached somewhere in the middle of the travel.
Next we rack out the focuser to close to focus position and see it does lie somewhere in the middle of the focus travel.
Conclusion so far anyway is that 1) We are close to decent collimation and 2) We can reach focus pretty easily with room in front and behind. That is a huge relief! Now onward and upward!
The 16 is powered up with covers off, ready to work!
Thanks for reading!