Eastern Limb Huggers

Lunar craters Humbolt and Hecataeus
Sketch and Details by Frank McCabe

Two old large craters near the eastern limb of the moon were putting on such a nice show at sunset that I could not resist sketching them. First was the floor fractured crater Humboldt (207 km.). This is an ancient Upper Imbrian period depression on the lunar surface. The mountain range in the center of this crater was catching the last rays of sunlight while the northeastern rim was already consumed by darkness as was most of the crater floor. Along the limb below Humboldt to the north in the eyepiece is the Nectarian walled plain crater Hecataeus (167 km.). The floor of this crater was completely in shadow while the inner, far, steep wall was directly illuminated by the sun and showing some interesting structure and texture.

Sketching:

For this sketch I used: white sketching paper 12”x 9”, HB, 4B, 6B graphite pencils, a blending stump and a plastic eraser the sky was darkened using black Conte’ pencil. After scanning, Brightness was decreased (-2) and contrast increased (+2) using Microsoft Office Picture Manager.

Telescope: 10 inch f/ 5.7 Dobsonian and 6 mm eyepiece 241x
Date: 11-3-2009, 4:45 – 6:00 UT
Temperature: 7° C (45° F)
clear, calm, low humidity
Seeing: Antoniadi III
Colongitude 99.1°
Lunation 16 days
Illumination 99.8 %

Frank McCabe