Ancient, Hammered, and Crushed

Crater Wilhelm West of Tycho
Sketch and Details by Frank McCabe

Last evening I was experiencing clear yet cold conditions for sketching. With skies expected to remain clear until after midnight and the moon high in the southern sky I chose a sketching target near the terminator just west of Tycho and north of Longomontanus. This region is part of the ancient highland crust of the moon and many of the craters here are very old, battered and partly hidden by younger impacts. I centered this sketch on Wilhelm (108 km.) a Pre-Nectarian crater that is somewhat difficult to trace on its western wall with several 20 km. craters there crushing the rim. Multiple impacts hammering on the east floor along a ridge was clearly evident. Immediately to the south of Wilhelm the remains of crater Montanari (77km.) could be seen. All parts of the south wall of this crater are hidden by layers of impacts all the way to Longomontanus (not in the sketch). I also included in this sketch to the west of Wilhelm the third Pre-Necterian crater Lagalla (85km.). Again most of the south wall is beaten down.

In the lighting provided by proximity to the terminator this was a rewarding area of the moon to observe and sketch. I stopped when my fingers went numb after 4 short breaks to warm up. It was a beautiful night to observe the moon as long as you were dressed for the cold.

Sketching:

For this sketch I used: White CPP sketching paper, 9”x 12”, HB and 4B charcoal pencils, a blending stump, gum and pink pearl erasers. After scanning, Brightness was slightly decreased (-2) and contrast increased (+2) using Microsoft Office Picture Manager.

Telescope: 10 inch f/ 5.7 Dobsonian and 6mm eyepiece 241x
Date: 1-6-2009 1:30 – 2:50 UT
Temperature: -8° C (17° F)
clear, calm
Seeing: Antoniadi III
Co-longitude: 26.8°
Lunation: 9.55days
Illumination: 67.1 %
Phase: 70°

Frank McCabe