Tuesday night, when I'd looked forward to getting a good look at the Orientale basin, was cloudy, but Wednesday night was crystal clear in Los Altos, and the libration was still favorable, so a few hours after moonrise, I set up the VX102 and decided to see what I could see in the Orientale Basin, even though the terminator was long past.

Looking at the limb of the just-past-full moon, the limitations of a 4" achromat start to become apparent. Violet haze (which usually isn't bothersome when looking at the terminator) was everywhere. So I experimented with filters. I don't have a minus-violet filter (maybe I should get one?), but my motley collection of filters bought from friends and swap meets includes a light yellow and an orange. The orange filter helped immensely, both with cutting glare and haze, and with increasing contrast to make the bright spots stand out. The light yellow didn't help much.

I have a hard time navigating on the moon at a high sun angle, since nothing looks like it does in the charts. I gradually learned that the small, intense white spots usually corresponded to small deep craters, larger, less well defined white spots were usually albedo features, and to look in Rukl's crater descriptions or at the whole-moon view on the flyleaf to identify the craters showing ray systems.

I drew a chart of what I saw, concentrating on accurate placement rather than artistic merit. (I might go back later and try to make a prettier version.) Once the sketch was drawn, I scanned it and then reversed it to match a real view:

http://www.best.com/~akkana/images/astro/orien610.jpg

I'm still not sure about all the identifications -- Eichstadt looks suspiciously closer to Cruger than to Lacus Veris and Lacus Autumni -- but Eichstadt had looked very prominent and deep two days earlier, and no other crater in that area looks like it ought to produce such an obvious white spot. Obviously I need to spend more time learning to navigate on a high-sun-angle moon.

Before giving up, I took a quick look at the other side of the moon. The eastern Crisium area is quite interesting at when librated away from us: a large crater with an unlit floor (perhaps Condorcet?) was right on the edge and looked like something had knocked a huge wedge out of the limb of the moon. This area was much more difficult to draw and I'm not going to share my failed attempt. :-)

As for observing Orientale with a terminator: July will also have a good libration at about the right time, and perhaps the weather will be better. You know what Terminators say: "I'll be back."