Ray Crater Proclus
Sketch and Details by Frank McCabe
Bright rayed crater Proclus (28 km.) lies between the highland Marsh of Sleep (Palus Somni) and the lowland Sea of Crisis (Mare Crisium). Proclus is a young crater about the same age as large crater Copernicus. But unlike Copernicus, the Proclus impact event arrived at an angle less than 15° from the west southwest based on the butterfly wing pattern of debris seen on the lunar surface. This pattern can be seen again on the eastern side of the moon several hundred kilometers to the south of Proclus with craters Messier and Messier A (not drawn here). The gray area to the upper right of Proclus is Palus Somni inside the “forbidden zone” where no rays can occur in the uprange direction. See chapter 10 of “The Modern Moon” by Charles Wood, Sky Publishing Corporation, for a more complete explanation. The rim of this crater in the high sunlight was as brightly illuminated as the rays. This crater is nearly as bright as larger Aristarchus across the lunar nearside to the west. Like crater Tycho this is one of those craters that are most impressive at high sun even with a modest size telescope. More than a lifetime of observing and even sketching awaits the amateur astronomer on moonlit nights.
Sketching
For this sketch I used: black Strathmore 400 Artagain paper 12”x8”, white and black Conte’ pastel pencils and a blending stump. After scanning, Brightness was decreased (-6) and contrast increased (+5) using Microsoft Office Picture Manager.
Telescope: 10 inch f/ 5.7 Dobsonian and 6 mm eyepiece 241 x
Date: 7-16-2008, 4:20-5:45 UT
Temperature: 25° C (76° F)
Clear, light winds
Seeing: Antoniadi III
Colongitude 67.6°
Lunation 13 days
Illumination 95.8 %
Frank McCabe