Ever since I had my first decent telescope, one of the ubiquitous 2.4” Japanese refractors of the 1960s, I was fascinated with looking at the cusps of the crescent moon, what my father liked to call “a fingernail clipping” moon. I particularly liked the detached bits of light at the very tip wondering what it was that I was seeing.
We have just such a view here. In the center of the image is a crater within a crater. This is Boussingault (72km dia) comprised of Boussingault-A and Bossingault-G. Closer to the limb is another well seen crater, Neumayer (78km). Between these and a little farther up the crescent is Helmholtz (99km). These craters are usually not this well seen but we have a favorable libration here where this region is tilted a bit more towards the Earth.
Farther on down the cusp, towards the tip, you can just make out a large crater partly in shadow. This is Demonax (117km). Below this is a bright clump that is the convergence, the uplifted merge of the walls of Demonax and Scott (111km) which is in deep shadow, with the last bit of light being the far wall of Scott. Beyond that completely in shadow is the crater Cabeus which was famous as the impact point for LCROSS (Lunar Crater Observation and Sensing Satellite) which was launched together with the Lunar Reconnaissance Orbiter (LRO) but independently ended its mission with that impact on Oct. 9, 2009. I was on one of the teams looking for evidence of the impact with a large echelle spectrograph on the 61” Kuiper Telescope on Mt. Bigelow north of Tucson, AZ. Sadly we did not detect any “splash” in the wavelength we were observing but I became intimately acquainted with Cabeus!
With these as landmarks the reader can explore, here or better with a telescope, and find many more craters that are not normally seen when looking at something larger than just a lunar crescent.
