Mid-Moon Craters

Lunar craters Arzachel and Alpetragius
Sketch and Details by Frank McCabe

With the moon just past first quarter, many beautiful, deep craters near the center of the lunar-earth facing side standout in shadowed relief. Among those visible were the famous trio of Alphonsus, Ptolemaeus and Arzachel. During this observation I selected Arzachel (96 km.) and neighbor Alpetragius (41 km.) for sketching. Both of these craters were on display about 200 kilometers from the terminator shadow line. Arzachel is the southern most of the above mentioned trio. It is a lower Imbrium impact depression and in addition it is floor fractured. Central to the crater floor is a fine mountain projecting one and a half kilometers above the floor. Also on the floor of the crater is Arzachel A (10 km.) with light shimmering off its illuminated rim. Part of Rimae Arzachel was visible as a bright edge rille which partly paralleled the floor shadow cast by the northeastern rim.
Alpetragius the smaller, older crater (Nectarian) has a very large round mountain covering most of the crater floor. Just the tip of this mountain was catching the first rays of morning sun as I began this sketch.

Sketching:

For this sketch I used: black Strathmore 400 Artagain paper 8”x 8”, white and black Conte’ pastel pencils and a blending stump. After scanning, Brightness was decreased (-2) using my scanner.

Telescope: 4.25 inch f/10 equatorial and 6 mm at 180x
Date: 5-3-2009, 0:50 – 1:40 UT
Temperature: 13°C (55° F)
hazy, high thin clouds, calm
Seeing: Antoniadi III
Colongitude 11.2 °
Lunation 7.9 days
Illumination: 63 %

Frank McCabe