Hitchhiker's Guide to Rukl Chart 44
CCD images of Ptolemaeus (bottom), Alphonsus (center) and Arzachel (top)
at first quarter (left) and at last quarter(right).
Robin Casady's CCD images of Ptolemaeus (left) and Arzachel (right).
See also an impressive
of the area at
(JRF <freeman _at_ netcom.com>)
- This prominent trio of craters -- Arzachel is on Rukl chart 55 --
are a major "landmark" feature, easily recognized and useful for
orientation, for the great southern peninsula that dominates the
south-central portion of the Moon's visible disc. Alphonsus and
Arzachel have rilles in their interiors.
- Alphonsus (David North <d _at_ timocharis.com>)
A rare and fascinating event was watching, bit by bit, sunrise over
Alphonsus. At first sight, it was nearly completely dark other
than the rim, but it lit up over a surprisingly short time. At one
point, the central peak looked like the gnomon of a sundial, with a
perfect ray headed off at three o'clock...
- There is also an
Selected Areas Program page on Alphonsus.
- Ptolemaeus at Sunrise (David North <d _at_ timocharis.com>)
1/31/2001 around 6pm PST:
It looks like there's something dimly lit (but kinda
largish) near the lower center of Ptolemaeus
(or whatever large crater is where you would roughly expect it to be
-- a bit south of the equator.
Things can't be dimly lit on the moon...
For more detail and sketches, see
Mark Taylor: I was thinking about a jaggedy surface lit just at
the tips of the jaggies, so you see a (laser-printer-style) gray
David: The more I think about it, the more I like this.
Combined with the arc
of the bottom of the crater ... it lights from the center out, in
obviuos rays (at least on nights like this) and other craters don't
But considering your suggesting, I'd guess that's the "root
methodology" here, though I don't recall seeing anything similar in any
of the other big plains.
- Ptolemaeus at Sunrise Bill Arnett
7/9/00 1:43 AM PDT:
I noticed that the Sun was about to rise over
Ptolemaeus. About midnight I checked again and still nothing but a spot of
light on the far (western) rim. But as the Moon sank lower in my sky, the Sun
rose on my target on the Moon and the race was on! At first I thought I could
see a slight brightening in the middle of the floor. I went in for a while to
see if anything would change. By a little before 1am there was a very neat
quartet of bright streaks in the middle of the crater floor. I interpret
these as the Sun shining thru low valleys in the eastern rim onto a dome
shaped floor (perhaps the dome shape is due to the spherical nature of the
Moon?). As the Moon sank lower the rays got brighter and wider. By the time
it disappeared below my neighbor's roof (only 4 degrees up :-) the rays had
merged together and about half the crater floor was bright except for a long
shadow from one of the easern rim peaks...
- Ptolemaeus Rays
(<bruceh _at_ mdhost.cse.tek.com> Bruce Harrington)
June 12, 1997, with a Takahashi FS60 60mm,
a bit after sunset (~9:30 PDT, 0430 UT 6/13), through scattered clouds.
Starting at ~20x
("finder mode"), I noticed a smudge in Ptolemaeus.
At ~0445 UT using 100x, I saw
FOUR distinct rays: a set of three to the south, a wider dark band, and a single
ray to the north. I could have these directions backwards. The combo of mild
dyslexia and a star diagonal... :) . The sun side of the peak causing the wide
dark band was visible as a bright white dot. I was able to watch this off and
on (due to the clouds) until 0530 UT, when the clouds got serious and I packed
it in. By that time, the group of three rays had merged, so the shadow outlines
of peaks no longer extended entirely through the light area. The north ray was
- Muller (Randy Muller <71172.1234 _at_ compuserve.com>)
Crater Muller made a nice little inverted Mickey-Mouse shape with its
two small ears (A and O). This crater is halfway between Ptolemaeus
and Hipparchus. Not a large or prominent crater, Muller is surrounded
by giants from astronomical history.
- Sinus Medii (JRF <freeman _at_ netcom.com>)
- The southern part of Central Bay is crossed by unnamed rilles.
- Klein at Sunrise (...Akkana)
UT 5/11/2000 at about 0545:
Klein, straddling the terminator at 5:45
UT, looked like it had an embedded crater in it, almost exactly
concentric with the main crater. It was probably a trick of the light
-- Rukl's sketch shows no such feature in Klein, just a curved central
peak which might have looked like part of a concentric inner ring.
There was a nice catena leading into Klein across the northwestern wall
This page last modified: Oct 03, 2011
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