L49: Gruithuisen Delta & Gamma

Sketch made on 22 November 2015, UT 17:00, using a Sky-Watcher 10″ and a TeleVue Nagler zoom 3-6 mm. Seeing improving to 4/5. South is up.

Lunar domes Mons Gruithuisen Delta and Gamma can be found in the moon’s northwestern quadrant, between prominent crater Mairan, and not so prominent Gruithuisen (neither of which are captured in this sketch). The two domes are the features in the center of the sketch, with Gruithuisen Delta to the left and Gruithuisen Gamma, which has been said to resemble an upturned bathtub, to the right.

During the observation my eye was drawn to a small feature just north of Gamma. It actually consists of two small adjacent craters, but with the sun angle at the time of the observation, they looked like one crater Timaoes bridgewith a very thin and shiny white ‘bridge’ traversing the darkness of the crater’s interior. The view was truly mesmerizing, especially as the feature after some time seemed to detach itself from the crater wall. There is of course the infamous O’Neill’s bridge on the western shore of Mare Crisium, and it struck me how easy it is to be fooled by the moon’s ever changing lightning conditions.

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