Stand Alone Crater

Eratosthenes Crater
Sketch and Details by Frank McCabe

Crater Eratosthenes rests on the boundary between the Sea of Showers and the northwestern extension of the Sea of Islands known as the Seething Bay. This crater is a magnificent stand alone crater. It is 58 kilometers across and nearly 3.7 kilometers deep. Eratosthenes began as a small mountain size rock impacting the moon at the end of the Apennine mountain range onto the mare basalt. This event occurred 3.15 billion years ago and defines the beginning of the Eratosthenian period. Other well known craters forming at about the same time include Langrenus and Bullialdus.
Eratosthenes is a regal feature when illuminated with the terminator nearby. Its terraced inner walls, irregular rubble strewn floor and central peaks make it a most attractive sight in telescopes of all sizes. See for yourself at the next opportunity.

Sketching:

For this sketch I used: black Strathmore 400 Artagain paper 9”x12”, white and black Conte’ pastel pencils and a blending stump. After scanning, Brightness was decreased (-4) and contrast increased (+4) using Microsoft Office Picture Manager.

Telescope: 10 inch f/ 5.7 Dobsonian and 6 mm eyepiece 241x
Date: 8-11-2008, 1:15-2:30 UT
Temperature: 20° C (68° F)
Clear, calm
Seeing: Antoniadi III
Colongitude 26.0 °
Lunation 9.8 days
Illumination 72.3 %

Frank McCabe