Fabricius and Janssen
Sketch and Commentary by Frank McCabe
On this evening of observing the young, spring, crescent moon just past nightfall, I was preparing to sketch crater Santbech when my eye was drawn to the terminator region of the Vallis Rheita and on south. Back in February of this year I caught this region at a time near sunset but this evening I was looking at an opportunity to capture an interesting crater rim illumination as long as I began drawing quickly. Along the terminator to the south of the valley is Nectarian crater Metius. This 90 kilometer cavity was completely in shadow except for its rim which was well displayed in morning light. Immediately south-southwest young 80 kilometer crater Fabricius was also displaying most of its rim. What captured my attention to this area initially was the way the light was illuminating the shared arcing walls between Fabricius and its neighbor Jannsen. The Jannsen component of this illuminated arc appears to be the centrally located slump block that dislodged at the time of the Fabricius forming impact (see: The Modern Moon by C. Wood page105). To the east of Pre-Nectarian crater Jannsen the paired craters Steinheil (70km.) and Watt (68km.) were putting on a show of their own. The shadows demonstrated the greater depth of Steinheil when compared to Watt. Finally on to the south along the terminator crater Rosenberger C at 48 kilometers marked the end of the large crater collection along the terminator in this sketch.
For this sketch I used: black Strathmore 400 Artagain paper, 8”x 11”, white and black Conte’pastel pencils and a blending stump. Brightness was slightly decreased (-4) and contrast increased (+5) after scanning using Microsoft Office Picture Manager.
Telescope: 10 inch f/5.7 Dobsonian and 9mm eyepiece 161x
Date: 4-10-2008 0:30 – 2:00 UT
Temperature: 4°C (40°F)
high clouds, calm
Seeing: Antoniadi III
Co longitude: 320.6°
Lunation: 3.9 days
Illumination: 20.4 %
Observing Location: +41°37′ +87° 47′