Sunset Terminator Across Mare Crisium

Mare Crisium is that interesting isolated sea on the northeastern side of the visible lunar surface. Only about half of it was visible during this sketching session.
The Nectarian Period event that formed this feature occurred more than 3.8 billion years ago. The mare portion of the basin is about 500 kilometers across. In the grazing sunlight across the floor, wrinkled ridges were visible in the north to south direction. Also on the western floor craters Picard (24 km.), Peirce (19 km.) and Swift (11km.) stood out in the low light. I could clearly see the lighter colored bench lava that partly buried craters here such as Yerkes (37 km.). Tall flat top mountains (massifs) beyond the shore stand at 2-5 kilometers above the sea. Also beyond the sea to the West crater Proclus (28 km.) with its remarkable bright rays was reflecting some sunlight.

Sketching:

For this sketch I used: 400 series black Strathmore Artagain paper 9″x 12″, white and black Conte’
pastel pencils , and Conte’crayons, a blending stump, plastic eraser. Brightness was decreased -2 and contrast increased +1 using the scanner for this sketch
Telescope: 10 inch f/ 5.7 Dobsonian with 6mm (241x)
Date: 12-23-2010 10:00 – 11:30 UT
Temperature: -8°C (18°F)
Weather: clear, calm
Seeing: Antoniadi III
Co longitude: 120°
Lunation: 17.7 days
Illumination: 94.5%

Oak Forest, Illinois

Frank McCabe