Mare Orientale

Session name: 20081015.2024
Equipment: Takahashi FS-102 refractor
Location: Drip Rock
Conditions: Scattered clouds, clear by Moon and calm air, mild temperature in the 60s.
Seeing: AII - AIII
Transparency: Decent
Traffic flow: very low (qty - 5)

Photo caption: Pete Lawrence's images of Mare Orientale on iPhone from Central Park

I was encouraged for this session after discovering the Pete Lawrence photos of Mare Orientale via a circuitous route in the lunar-observing yahoo group. In fact, I used the image to properly identify the features I could see in the eyepiece even if it was a day's difference. Later, a passerby stopped when I was packing. We chatted and he asked some questions about the moon. To show him what I was observing I whipped out the iPhone to display the very feature I scrutinized.

The concurrence of favorable libration, a proper phase, clear weather, and a reasonable hour is not too common. In my observing career, I only have a few observations of Mare Orientale, this one not the best. At the beginning of the session while the scope cooled down, there was some boiling seen along the limb. As the Moon climbed higher and the scope cooled down and the moments of steady seeing increased, the observation offered more detail.

East of Lacus Autumni, I observed two peaks on the limb. The outer one (north/Montes Cordillera?) was more prominent and a sharper shape compared with the nearby inner peak (Montes Rook?). For the inner peak, the side closest the northern peak appeared to have a gradual rise from behind the ridge of Montes Cordillera and at the peak a small indent or cleft was observed which then the wall fell sharply. What appeared to start from the outer peak, a ridge ran parallel inside of the moon limb for good length, about ~2 1/4 ~ 2 1/2 Lacus Autumni-lengths. This ridge was interrupted by the crater Eischstadt. The ridge I suspect was Montes Cordillera. Further south along the limb, I saw two small humps that I assumed were the corresponding peaks of the pair north. My notes describe these as undulations and not as pronounced as the pair above. Contrasting with the northern pair, the inner peak of the southern pair has the sharper, peaked figure.

What did the Moon like this evening? Check astromick's shots