by Marek Cichanski
Well, I was surprised how much fun Dennis and I had observing under such a bright moon tonight. We had some incredible seeing, and got surprisingly good views of a number of objects.
There was a nice hour or so of moon-free sky after sunset, although the moon rose around the time that it would otherwise have been astro twilight. Still, there was time to look for a few DSOs.
For me, tonight was an extended test of the new ED80, and I continued to be blown away by how well it performed. First, before the moon rose, I put on a new 22mm Nagler and enjoyed some wide-field views. And I do mean enjoyed! That eyepiece framed the Pleiades, the Double Cluster, and M31 each beautifully. Had most of M31 (including the spiral arms) and its two satellites in the field.
I went after M79 to see how it would do on a not-very-spectacular Messier glob, and it did pretty well. I couldn't quite resolve any stars, but the outer parts of the cluster had a mottled appearance. M76 and M77 were also very nice. Although stars aren't as bright in the ED80 as they are in my 6" Mak or 10" dob, the pinpoint-ness of them seems to me to make up for it to a large degree, somehow.
The seeing was just suberb nearly all night. No naked-eye twinkle to the stars at all, as far as I could tell. Dennis had a view of Saturn through his TV-102 that was unreal. Absolutely rock-solid, with laser-cut detail. Not a twitch. I decided to use this opportunity to see how far I could push the ED80 under this seeing. I looked for a tight double, and found Eta Orionis as a good test case. According to Karkoschka, it's got a separation of 1.7", with mag 4 and 4.9 stars.A 3" scope has a theoretical Dawes' limit of 1.5", according to my copy of All About Telescopes. Eta Orionis split very nicely, although it was very tight. I used a 5mm type 6 Nagler on a 2x Meade shorty barlow, for a total magnification of about 240x - that's about 80x per inch of aperture in this case. There were two perfect little white Airy discs, alternately touching and separated by blackness. I saw a black line between them probably a dozen times in several minutes of observation.
Rigel also split very cleanly, with the faint companion clearly seen. I tried Sirius at 240x, but no joy. However, there was joy in the fact that there was no colored halo around Sirius. Some scintillating blue and red color mixed in with the white, but that was it. Bright stars have a bit of a patriotic red, white, and blue color, but that's all she wrote. At 80x per inch of aperture, the diffraction ring pattern is maybe a tiny bit off-center, but even that impression was a bit questionable, as it seemed to vary a little bit with time. Maybe tube currents.
The seeing stayed good when I switched over to Jupiter, and I had a view of Jupiter that knocked my socks off. I know that this sounds crazy, but I think that I saw as much detail on Jupiter as I've ever seen with any of my scopes. And that includes my 10" dob under good seeing with top-notch collimation. I know how nutty that sounds, but I swear that was my impression. I was just stunned at the detail I was seeing on Jupiter - I was using 120x, occasionally 240x. Ditto the moon. Dennis also remarked on the utter lack of color on the moon. Not even any yellow. Mare Crisum, Langrenus, Petavius, Stevinus, and Furnerius were unreal, all lined up on the sunset terminator. Awesome!
Tonight continued the theme of "I can't believe how well this little 80mm scope is performing". I hate to prattle on about it like this, but I'm just amazed. I think that pretty soon everyone's going to have one. We'll probably start to see them being used as finders on big SCTs (credit for that idea goes to Dennis).
Well, I'm about to pass out, so I'll sign off and get horizontal. If it's good again tomorrow (Sunday), I may go to MB again.
Posted on sf-bay-tac Sun Feb 8 01:50:50 2004 PT
Converted by report.pm 1.0 Sun Feb 8 08:41:37 2004 PT