Janssen at 195 kilometers in diameter is a large ancient (4 billion year old)
walled plain crater in the southeastern highlands and is not far from the lunar
limb. Relentless moonquakes and solar system debris impacts have given this crater
its old look. The floor of Janssen is covered by numerous smaller craters. Without
trying too hard I could see 20 crater including those down to a few kilometers in
diameter. The center of the crater appears to bulge higher than the worn rim. Much
of this could be debris from the large much younger impact crater Fabricius (79
km.). Fabricius is an Eratosthenian period impact crater. It clearly shows steep
sloping walls and exhibits a central mountain range that is about 11 km. long and
also a long central ridge that is more than twice that length. Geologists tell us
that much of the debris across the floor of Janssen is Nectaris impact ejecta;
fluidized where the floor is smooth and irregular boulder-like where the floor
appears tortured. But perhaps the most interesting feature here is 140 kilometer long Rimae
Janssen. This rille looking like a graben, where it cuts through the high central
region south of Fabricius. It then narrows suddenly before reaching the rim in the
relatively smooth region of the floor. Pits that are visible via high resolution
images in these narrow regions imply volcanism. There is at least one dome on the
floor of Janssen but I was not successful in spotting it in the current
illumination. Craters Janssen and Fabricius presented fascinating features to
examine during this observation.
Sketching:
For this sketch I used: black Strathmore 400 Artagain paper, 7”x11”, white and
black Conte’ pastel pencils and a blending stump. Brightness was slightly decreased after
scanning.
Telescope: 10 inch f/ 5.7 Dobsonian and 6mm eyepiece 241x
Date: 9-29-2007 6:15-7:15 UT
Temperature: 16°C (60°F)
Clear, calm
Seeing: Antoniadi III
Co longitude: 122.1°
Lunation: 17.73 days
Illumination: 91.4 %
Frank McCabe
THAT is just a truely amazing sketch Frank!!
AWESOME!
Nice one Frank, I was working in that neck of the Woods on Friday night sketching Watt & Steinhill. A lovely area that was illuminated to perfection. You have captured it delightfully.
Go well, Dale
Wade and Dale,
Thank you both. I really enjoyed doing this one. Very pleasant night.
Clear skies to you both.
Frank
You have a gift to draw the moon, Frank. Fantastic!!!