A very favourable libration for the lunar south pole. Libration is the oscillation of the moon, by which parts near the edge of the disc that are often not visible from the earth sometimes come into view. In lunar astronomy, libration is the wagging or wavering of the Moon perceived by Earth-bound observers and caused by changes in their perspective. In the most favourable libration for the south pole, earth-bound observers can see 6-7 degrees beyond the south pole for short periods of time. It is this reason that leads me to conclude that I have finally found Shackleton, on whose flank lies the lunar south pole.

Cysatus and Gruemberger are at bottom on the northern flank of Moretus. Curtius to the left and Klaproth and Casatus (in shadow) to the right. Behind or poleward of Moretus is Short, whilst further towards the pole are the overlapping members of Newton. The back wall of Newton A is increasingly illuminated as the sun rises over the east wall of Newton A. Cabeus lies in deep shadow. On the left (east) edge of this image Simpelius and Schomberger lies north of (below) craters Scott and Amundsen, names that honour earth’s south pole explorers. Further poleward lie Nobile and Shoemaker. The Malapert Massif separates the Malapert crater from the Haworth crater that lies in deep shadow on the pole side of the massif. The elevation change between the Malapert Massif and the continuous drop to the floor of Haworth crater is around 8 km, equivalent to the height of Mt Everest above sea-level.

Shackleton crater (named after Antarctic explorer Ernest Shackleton) lies within the South Pole-Aitken basin, on a massif. The peaks along the rim of Shackleton crater are exposed to almost continual sunlight (i.e. never shadowed by earth’s shadow), while the interior is perpetually in shadow. The low-temperature interior of this crater functions as a cold trap that may capture and freeze volatiles shed during comet impacts on the Moon. Continuously illuminated mountains have been termed peaks of eternal light (pics de lumière éternelle, as poetically named by French astronomer Camille Flammarion) and have been predicted to exist since the 1900s.
Shackleton crater has also been proposed as a future site for a large infrared telescope. The low temperature of the crater floor (about 90 degrees Kelvin or minus 183 Celcius) makes it ideal for infrared observations, and solar cells placed along the continuously illuminated rim could provide near-continuous power to the observatory. About 120 kilometers from the crater lies the 5-km tall Malapert Mountain, a peak that is perpetually visible from the Earth, and which could serve as a radio relay station when suitably equipped.

Skywatcher 8 inch/f5 Newtonian.
ASI1600mm Pro, Televue Powermate 5x (focal length ~7000mm).
250 (2.6%) of 9378 frames stacked to maximise signal/noise ratio.
Backyard, Lysterfield, Melbourne. 22-05-2021.