A Planet, a Planetary, a Cluster, and Orientale

by Michael Portuesi


We had a clear night here in San Francisco, so we took good advantage of the situation. My 15" truss-tube Dobsonian has been sitting forlorn in storage since fall; it seemed almost criminal that it was getting no attention. So we assembled the scope in front of my house and did some sidewalk astronomy.

Saturn was nice under better than average seeing with a 20mm Plossl (96x) and a 7mm Orthoscopic (274x). The high power view was mostly clear, but had moments of soft seeing. The rings were clear, with the crepe ring and Cassini Division easily visible and the A-ring noticeably darker and dustier in color from the B-ring. I notice Saturn's north pole seemed obscured by the ring, and a little bit of a shadow was present around the planet's southeast pole. The planet itself had the usual orange band near the equator, though the southern hemisphere seemed a bit darker/grayer than the north. Five moons were visible; Hyperion, Dione, Rhea, Tethys, and Titan.

No sooner had we set up the scope than we got our first crowd of sidewalk visitors. One was a woman who was celebrating her 79th birthday today. We helped her climb the stepstool to the eyepiece, and after a few tries she was able to see Saturn. She was very curious and asked much better questions than the children who brought her! We told stories about Titan and the Huygens probe.

My Telrad was mounted improperly on the base, putting it out of alignment. When aimed at Saturn, it put the scope on NGC 2392 (The Eskimo Nebula) instead. I didn't think it would be visible from an urban location. So we showed it to our guests and took the time to observe it with an O-III filter. Without, it seemed a fuzzy star. The O-III made the nebula larger and more noticeable, but did not bring out additional detail (20mm Plossl, 96x).

Our Cambridge Star Atlas indicated the open cluster NGC 2420 was also nearby. After failing to find it with a 32 Erfle (60x), we drew up a chart with SkyTools to discover it shared the FOV with Saturn. Just a little bit off to the east of the planet was a dim little sprinkling of stars, forming maybe the shape of an iris or some other flower.

Finally, it was getting late enough to see the Moon, and to observe Mare Orientale. With the 12.5mm Ortho (154x) the view was miserable due to bad seeing from air currents from nearby houses. But we still got a view of the Mare itself. I went inside to get the Downstairs Rukl, and we identified Lacus Autumni, Lacus Veris, and the Mare itself on the very edge of the limb as a slight darkening. We also observed a bright patch above Lacus Veris which we suspect might have been the Rook mountains, but we weren't sure.

Close to midnight, we broke down the scope and packed up. We got planetary, deep-sky, and sidewalk astronomy done in one night. Not bad!


Posted on shallow-sky Jan 30, 2005 00:29:46 PT
Converted by report.pm 1.2 Jan 30, 2005 18:34:29 PT