Mar 2016

Starry "mountains" appear in Lunar Cusps

Crater Rims Illuminated by Lunar Sunrise: These points of light beyond the sunlit cusps of the Moon look like solitary peaks lit by a low Sun, but they are not. They are probably higher elevations of portions of crater walls protruding above the surrounding lunar terrain which consequently catch sunlight. I regularly check the cusps of the illuminated Moon for these features and on Mar 11, there appeared one of the brightest examples I have seen. There are several additional fainter spots as well I count at least 5.

While there are isolated mountains on the Moon that can catch the rays of the rising sun, they are usually found in maria in the northern hemisphere (Mt. Pico, Mt. Piton, Teneriffe Mtns, etc). There are no lava plains with isolated mountains on the southern polar regions of the Moon. In the south, the Moon presents a profile that is much more rugged than in the north with crater piled on to of crater and only low mountains in crater centres. I tried to determine which feature might be producing these effects from a detailed lunar map and there is more than one candidate but they are all craters and no isolated mountains.

Celestron EdgeHD 9.25” with Canon 60Da at prime focus, foc.len. 2350 mm, f/10. The FOV of this scope is just a bit too small to get the entire Moon in a single frame. This was a 2 second shot at 640 ISO and shows Tycho dimly glowing with earthshine.


This image is a pair of images taken at the same time that have been stitched together to give the entire crescent. Both cusps are interesting but only the southern one (lower left) had the sunlit “peaks” the brightest showing up as a faint dot in this image at the lower left. This image was taken with same equipment but was only 1/20 s to avoid over-exposing the details of craters on the sunny surface. Mare Crisium is the largest circular structure at the widest part of the crescent. Lots of interesting detail was visible in the telescope views along the terminator. Both images Ⓒ John Hlynialuk