Hitchhiker's Guide to Rukl Chart 45

Albategnius Robin Casady

Each time I went out, Albategnius was different. Klein's wall slowly emerged from the shadow. By midnight much of the floor was illuminated and long pointed shadows pointed inwards from the peaks on the rim. Albategnius B was apparent, though its floor was dark. It was fun to watch the light slowly spill into Albategnius.

Albategnius (David North <d _at_ timocharis.com>)

Look for shading in the floor of Albategnius, and for two depressions. The latter looked awfully subtle to me the time I noticed them; I assume they are older (or for some other reason, shallow) craters.

Albategnius (...Akkana)

Albategnius seems to be crossed by many north/south pointing rilles and catenae -- in addition to the catena leading into Klein, there's another very prominent rille on Albategnius' eastern wall. Perhaps these are secondaries from Copernicus, or even from Imbrium (though they're presumably younger than that)?

Burnham Sunrise Ray (JRF <freeman _at_ netcom.com>):

Approximately as the sunrise terminator crosses Burnham, the rising sun shines through a gap in that crater's western wall, and creating a ray of light across the flat terrain lying between the west wall of Burnham and the east wall of Albategnius. This ray is finer and possibly longer-lived than the better-known Hesiodus sunrise ray. It has been seen in apertures as small as 70 mm. For predictions for it, see the RLO page on the Burnham ray.

Burnham will be hard to find at sunrise. This small crater is located at the southwest corner of Rukl's map 45, approximately at Selenographic latitude 14 south, Selenographic latitude 7 east. The obvious nearby landmarks for finding it are the great craters on the east side of Mare Nubium, but they will be in darkness. I suggest observers first locate the prominent crater pair Theophilus and Cyrillus, south of Mare Tranquillitatis (on Rukl map 46), scan west (toward the terminator -- that's Lunar west, not celestial west) for about one and a half times their combined length, to Abulfeda (on Rukl map 45), then crater-hop not quite that same distance west again, to find Burnham along the terminator. The small triple crater comprised of Vogel, Vogel B, and an unnamed crater adjoining Vogel to the south, may serve as a landmark.

See also the L'ALPA page on the Burnham ray (in Italian) for timing predictions.

Halley Sunrise Ray (Akkana)

In the same general area as Burnham, the crater Halley also exhibits a sunrise ray. The Halley ray seems to be a very short-lived phenomenon (it disappeared ten minutes after I first saw it on May 13, 1997 at about 8:10-8:15pm PDT, though I have no way of knowing when the ray first appeared since it was already well underway by the time I noticed it).

I observed the Halley Ray again on July 11, 1997 at about 9:15pm PDT. (The prediction for the Burnham Ray that night had been approximately 5pm.) Find Halley on the border between Albategnius and Hipparchus, the last and largest in a smooth arc of four or five craters of steadily increasing size which terminate at Halley (all of which will be lit except Halley, when the ray is occurring). The floor of Halley was dark except where it was bisected by a thick ray of light.

Sunrise Ray NE of Crater Hind (Larry B Smith <KTBNDRY _at_ paonline.com>)

I located a sunrise ray while observing the crater row Halley, Hind, Hipparchus C, and Hipparchus L. The ray was located to the southeast of the crater Hind and originated from an unnamed crater or depression at latitude 9.5 deg. south and longitude 9.2 deg. east. The ray extended 40 km to the west from the break in the "crater wall".
Observation: 01/09/03 at 18:28 EST ( 23:28 UT). The ray had widened considerably by 18:52 EST.
Instrument: 12.5" Dobsonian
Seeing: good to fair. Partly to mostly cloudy (thickening cirrus clouds were causing me considerable annoyance). e

Vogel Sunrise Ray (Akkana)

The Vogel Ray is a much more obvious phenomenon than Burnham, and lasts for hours. It is visible initially as a slim triangle of light extending down the side of Vogel; as time passes, the width of the triangle increases, but the length stays relatively constant. See my sketch at right.

Halley/Hind crater arc (Akkana)

Halley, Hind, and Hipparchus C and L make a nice arc of craterlets of decreasing size, very reminiscent of the craterlet arc inside Clavius. Find them at sunrise (roughly first quarter) starting at the junction of Albategnius and Hipparchus, and arcing away from the terminator.

Hipparchus (Steve Coe <scoeandlross _at_ sprintmail.com>)

Hipparchus--large crater, open on north side with fascinating floor. There is a "horseshoe" shaped central mountain, this is the only lunar crater I know with a central promentory that is U-shaped. A fresh, new crater is on the north side of Hipparchus, it is Horrocks. The south side of the floor is a jumble of large mounds and small ruined craters. Also on the south side is a miniature "Straight range" of mountains. The walls of Hipparchus are ruined in such a way that they appear like the knuckles of a giant fist, with smooth peaks and wide valleys in the wall. All in all a unique crater.

Descartes (David North <d _at_ timocharis.com>)

As I am currently slogging my way through all kinds of odd Cartesian geometries, and he was an enigmatic personality, it's only fitting that Descartes was the most interesting thing to see in this area. It's an old crater, somewhat ruined, but some of its curious history can still be read. Concentric with its battered walls (almost gone in the north) is a distinct rille-like ring. Rather than assuming two hits in the same place, this looks like a slumping fault, a sort of miniature of the effect we see in the huge rilles around the Maria, such as Humorum or Serentitatis. Or perhaps more accurately, the same effect that is so stunning in the larger Poseidonius.