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Field test of NGT-12.5 optics

Started by Inge_S, 02/06/2003 07:54AM
Posted 02/06/2003 07:54AM Opening Post
I'm a part owner of a 12.5-inch NGT recently purchased (second-hand) by the local astronomy club. The scope was picked up about a month ago, and we have had the scope out a few times to get acquainted with the set-up (mechanical and electronical issues). So far we have concluded that the potential of the scope is great, but we have to do some maintenance in order to have it working properly. During the first couple of observing sessions we have been 3 persons present, and checked out a few show objects. However, yesterday evening I had the opportunity to spend a couple of hours alone with the scope and used the chance to check the performance of the optics.

For some reason I could not find the power cable connecting the battery pack and the control unit of the scope. Therefore I had to move the scope manually. This was, of course, a drawback, but I was able to handle powers up to 280x without problems.

The sky was partially clouded (coverage varying from 40 - 70%) but seeing was excellent. The first test object was Struve 1126, a near equal 1" double in the same low power field as Procyon. This double was cleanly split at 280x.
Next target was Saturn. The image at 280x was sharp and contrast was great, showing much nice detail at the planet's surface, of course the Cassini division, the crepe-ring and a hint of Encke's division at the ends of the ellipsiodal image of the ring system.
Jupiter's surface was very bright at 280x, almost annoying, and it was necessary to spend some time to adapt the eyes in order to make out the fine detail at the planet's surface. Unfortunately there were no satelite transits taking place, but I followed a GRS passage during the observing session. This was my first chance to have a close look at Jupiter with 320mm aperture, and the amount of detail clearly exceeds what can be achieved with my 200mm Zambuto mirror (which is excellent, indeed).

The conditions were useless for observation of nebulae. Low clouds reflected a lot of high-pressure sodium light, so most of the time I spent observing doubles. Zeta Orionis was a great surprise. Normally it is very difficult to split it from my latitude, but this evening it was EASY. So were Theta Aurigae and Eta Geminorum, and for the first time in my life I could see 6 stars in the trapezium. A lot of other doubles in the 0.8" - 1.5" range were resolved with ease, e.g. 52 Orionis, 32 Orionis, Eta Orionis and Zeta Cancri which was a BEAUTIFUL triple system. The separation of the close pair is presently about 0.8". It was easy to see that the amount of dark space between the components is greater in the 12.5-inch than the 8-inch. I didn't challenge closer doubles this evening since I didn't have the RA-motor running.