Hitchhiker's Guide to Rukl Chart 44

Robin Casady's CCD images of Ptolemaeus (left) and Arzachel (right).

See also an impressive high-resolution shot of the area at astro-shop.com,

Alphonsus:

Arzachel:

Ptolemaeus (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 ALPO 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 the discussion on timocharis.com.

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 scale illumination.

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 appear to.

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.

Weird crater.

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 still distinct.

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 of Albategnius.