1/30 seconds exposure, Fuji Provia 1600 film.
14" f/10 schmidt-cassegrain telescope plus 7mm eyepiece.
When the moon is about 9 days old, a curious feature is visible in telescopes lagers than 3" aperture. This is known as the Straight Wall. It is actually a fault line, with one side higher than the other. When the sun has just risen, the feature shows as a dark line, as in the above photograph. This is due to the shadow cast by the cliff. About 10 days later when the sun is setting on the Straight Wall, it appears as a bright line as seen in the image below.
The Straight Wall is situated on the eastern edge of Mare Nubium near the crater Birt, and north of Tycho. It is about 120 metres high, and about 120km long.
This image shows the Moon from the Straight Wall southwards to Tycho. The crater to the left (east) of the Wall with the smaller crater on its western rim is Thebit. The crater on its rim is Thebit-A. Birt is the smaller crater to the right (west) of the wall, also with a small crater on its rim. (Birt-A)
The Straight Wall is situated on the eastern edge of Mare Nubium near the crater Birt, and north of Tycho. It is about 120 metres high, and about 120km long.
