Popular Astronomy

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2011-11-12

Evening at Eratosthenes

Observational drawings have been received from Sally Russell (Eratosthenes, 22 August) and Peter Grego (general lunar studies, July-September)—a low total, but only to be expected at the tail end of the usual mid-year lull in lunar observations. However, many excellent lunar images have been sent in by Mike Brown, Jamie Cooper, David Finnigan, David Scanlan and Larry Todd.

Sally’s observational drawing shows the evening terminator approaching Eratosthenes, a 58 km diameter crater near the western extremity of the Apennine Mountains. Eratosthenes is a prominent feature with complicated interior terracing and a nice group of central mountains (hidden by shadow in this observation). Although there’s a complete absence of a ray system, secondary impact structure can be traced in the surrounding terrain, with prominent concentric ridges that give way to narrow secondary impact grooves, some of which extend more than a hundred kilometres from Eratosthenes’ rim.

 

Added by:  Graham Sparrow