Sunset Terminator Approaching Atlas

Lunar craters Atlas and Hercules
Sketch and Details by Frank McCabe

Craters Atlas (87 km.) and Hercules (69 km.) made an attractive pair on this evening a couple of days past full moon. Atlas the older of the two (Upper Imbrium period) was deeper into shadow hiding the fractured floor but not the central floor uplift and peaks. The rims and aprons of both Atlas and Hercules were nicely illuminated as were the surrounding ejecta melts. Hercules the younger of the pair is an Eratosthenian period crater (3.2 billion years old). On the floor of Hercules I could see 14 km. diameter Hercules G near the center of the lava flooded, smooth floor. The sketch region extends southward (top of sketch) to the stand alone crater Grove (29 km.). To the north of Hercules is the 34 km. diameter crater Keldysh with its bowl shape and shadow hidden floor.

Sketching:

For this sketch I used: black Strathmore 400 Artagain paper12”x 9”, white and black Conte’
pastel pencils and a blending stump. After scanning, Brightness was decreased (-3) and contrast increased (+3) using Microsoft Office Picture Manager.

Telescope: 10 inch f/ 5.7 Dobsonian and 9 mm eyepiece 161x
Date: 9-18-2008, 4:00-5:30 UT
Temperature: 15° C (59° F)
Clear, transparent, calm
Seeing: Antoniadi III
Colongitude 129.3 °
Lunation 18.3 days
Illumination 90 %

Frank McCabe