by Mike J. Shade
Recently I picked up a Takahashi Mewlon 300 which is a 12" f/11.9 or so Dall-Kirkham Cassegrain and is the primary telescope in the observatory (replacing a 12.5 Ritchey-Chretian, which replaced a 14.5" RC, which replaced a C14 and so on). While the long focal length makes CCD work a bit involved, I decided recently to try it out visually. I will say that the optics on this telescope area about what you would expect from Takahashi, pretty darn good. While it does not possess all of the latest advances in telescope materials (the tube is aluminum and not carbon fiber and the optics are Pyrex and not some exotic material such as Astro-Sital), it is a fine telescope.
Since we are in late June, we are about ready to have our monsoon season where we get the famous AZ thunderstorms. However, the monsoon this year is late, so we have been blessed here with reasonably clear weather although there is some moisture around, at least it is not raining.
On the 26th of June I put this scope through its paces. The native focal length is about 3572mm so my 22 Panoptic gave about 162X and my 13 Plossl gives about 275X. I rated the transparency at 7 (1-10, 10 being perfect) and seeing a 7. The scope is coupled to a Paramount ME which is of course run via The Sky software. As a result my night vision was compromised a bit by having to look at the computer screen to get the telescope to slew around.
I started with M3, well placed near the zenith. With the 22 the view was absolutely stunning, very nice and crisp with a strong hint of resolution (it was not quite dark). NGC 5248 galaxy (gx) with the 22 showed a stellar core surrounded by an oval shaped disc of light. Within this oval area there were very subtle hints of changes in brightness. NGC 5466 a globular looked very much like an open cluster, being an irregular shaped ball of stars with several streamers radiating outward. Full resolution hinted at with averted vision. NGC 5529 gx, very dim and elongated, reminding me of a dim and small NGC 891. NGC 5557 gx, bright and circular, stellar core but what was striking to me was that it looked very "white" visually. Next I popped over to M5 and I must say that it reminded me of a sprinkling of salt on black paper with streamer flowing outward and full resolution with the 13. NGC 5921 gx was framed nicely by three stars of about even brightness with a bright core and a hint of "fogginess" around the core. Funny, with three hours of CCD exposure it is a really nice spiral. NGC 5736 gx very elongated, brighter core with the edges tapering evenly to the end. NGC 5775 gx is the brighter of a pairing with NGC 5774 which is a very dim circle of light. NGC 5878 gx lies in a sparse field with a stellar nucleolus oval in shape. From the dim and small, a change of pace was M13, of course big and bright with non symmetrical streamers. It was resolved. M10 was smaller than M13 but very round. I thought that M12 looked somewhat square with four distinct "legs" coming out of it. To round out the evening was the planetary nebula PK 10+18.2 and it was the most difficult object of the night. Basically it was a wisp, a very delicate wisp of light and very vague.
In summation, it was fun to spend some time actually looking at things. While I knew that this was a 12" telescope and my views were not likely to be outstanding, especially on dim NGC galaxies, I was surprised that it did as well as it did. And while the eyepieces have been replaced once again by the CCD camera, I suspect that there will be more forays into the land of visual astronomy, especially with Mars later this year.
Posted on sf-bay-tac Jul 01, 2005 19:08:54 PT
Converted by report.pm 1.2 Sep 26, 2005 19:43:37 PT