November 19, 2017
Originally published May 14, 2008
image by Stefan Lammel, Uxbridge, England, chart from Goodacre's The Moon; south up
A magnificent bay in the M. Imbrium, originally an independent Mare or vast mountain walled plain, whose original boundary on the S. side has disappeared. Its site being now indicated by low ridges not exceeding 100 feet in height and visible under a very low sun. The high curved mountain border on the N. terminates in two fine headlands, Prom. Laplace and Prom. Heraclides, the distance between these two capes being 135 miles. The mountains bordering this dark semi-circular bay are said to have peaks rising 15,000 to 20,000 feet above the sea. The area of the Sinus contains a number of ridges concentric with the shore, also many craterlets. Krieger shows no less than 40 of these delicate objects. There is also one conspicuous crater, A. A little N. of A I have found a short crater valley. No clefts have been found on the floor, but under a high light a number of bright rings develop with dark interiors, suggesting submerged craters. At the foot of the cliff a little E. of Sharp, I have seen a chain of round-topped hills like huge boulders.
CAW Note: Goodacre's description from 1931 holds up pretty well against modern imaging. Virtually all of the detail he draws within the sinus can be correlated with features in Stefan's image. The mountainous rim - the Jura Mountains - of the Sinus Iridum proved much harder to depict accurately and Goodacre mistakenly interpreted various topographic variations as craters. The crater Sharp is at far left; East and West have been reversed to accord with post-1960 usage. Goodacre's excellent book The Moon is now past the 75 years of copyright protection - I hope that the Project Gutenberg or some similar organization digitizes it and places it online.
17 Feb. 2008. 10in f4.8 Newtonian, Infinity 2-1M, 4x PowerMate, green filter, 19 ms, 370/2600, MAP: 108x64, Registax, PSE 5
Rükl plate 10
Yesterday's LPOD: Shafted!
Tomorrow's LPOD: Unfamiliar Territory