Category: Moon

Crater Mersenius
Sketch and Details by Frank McCabe

Mersenius is an 84 kilometer diameter floor fractured crater just to the west of Mare Humorum. This crater is a Nectarian period crater estimated to be 3.9 billion years old. Close examination shows it has a very noticeable convex floor which is estimated to be half a kilometer higher than the floor edge. No hint of any central peaks seemed to be visible. The floor of this crater is fractured and one of those rilles appearing as a fine bright line was in view when the seeing was at its best just a few times as I sketched. Lunar geologists suggest that the bulging floor is due to lava upwelling from basin lava (Humorum), which released molten rock through the floor fractures at the crater’s center. This may account for the burial of the central peaks and production of numerous rilles. The floor distance below the crater rim is about 2.5 kilometers. Parts of the Rimae Mersenius system stood out clearly northeast of Mersenius Other craters included in my sketch are Mersenius D to the southeast, P to the north, 34 and 42 kilometers in diameter respectively. This was a most enjoyable sketching session because of the seeing and weather conditions.

Sketching:

For this sketch I used: black Strathmore 400 Artagain paper 8”x11”, white and black Conte’ pastel pencils and a blending stump. After scanning, Brightness was decreased (-4) and contrast increased (+2) using Microsoft Office Picture Manager.

Telescope: 10 inch f/ 5.7 Dobsonian 6mm eyepieces 241x
Date: 10-12-2008, 1:00 – 2:45 UT
Temperature: 16° C (61° F)
clear, calm, humid
Seeing: Antoniadi III, II
Colongitude: 60.4 °
Lunation: 12.7 days
Illumination: 90.6 %

Frank McCabe

Crater Longomontanus
Sketch and Details by Frank McCabe

Over the past few weeks clear skies and good seeing have been absent at my usual observing site. Last evening all that changed at sundown with good clearing of the heavy cloud cover. As the moon moved eastward against the background stars and entered Capricornus, it was high enough in my sky for close examination and sketching. Among the craters of the southern highlands just at the terminator margin was walled plain crater Longomontanus (155 km. in diameter) basking in the early morning sunshine. This ancient impact is an old worn Nectarian period formation with a younger floor formed by liquefied eject from the formation of one of the distant large basins such as Orientale or Imbrium (see LPOD, December 30, 2007, C. Wood). Immediately east of Longomontanus I was able to see what remains of smaller older Longomontanus Z (95 km.). It is the darker shadowed depression that is only partly visible. The floor of this crater has small, mostly buried, central peaks which were casting long shadows on to the western inner crater wall. One of the three craters, Longomontanus L (16 km.) on the western floor stood out nicely in the grazing sunlight at the margin of the crater floor shadow to the north.

Sketching:

For this sketch I used: black Strathmore 400 Artagain paper 8”x11”, white and black Conte’ pastel pencils and a blending stump. After scanning, Brightness was decreased (-3) and contrast increased (+3) using Microsoft Office Picture Manager.

Telescope: 10 inch f/ 5.7 Dobsonian and 9 mm and 6mm eyepieces 161x, 241x
Date: 10-9-2008, 0:10 – 2:15 UT
Temperature: 10° C (50° F)
clear, calm, humid
Seeing: Antoniadi III
Colongitude: 23.4 °
Lunation: 9.7 days
Illumination: 65.9 %

Frank McCabe

Lunar Southern Highlands
Sketch and Details by Frank McCabe

I have always found the southern highlands an interesting region of the moon to examine along the terminator. At the times of low sun the craters here take on more unique and individual identities than at higher illumination. On this observing and sketching night, I managed to examine and sketch five notable craters. From south to north along the terminator are Boguslawsky (98km.), crater Boussingault E ( 98km.) and Boussingault B (54km.). All over the southern highlands are numerous, ancient, worn, soft looking craters between 10 and 90 kilometers in diameter. Some of the craters in this region pre-date the formation of the major lunar basins. These craters look soft and dusty with smooth terraces and regolith slumping to the crater floors. Lunar geologist Donald Wilhelms speculated that the appearance of the craters here is caused mostly by fluidized ejecta and debris tumbling down the crater walls to the floor. He also believes that the craters in the region of the sketch are sitting on an ancient 650 kilometer basin that is all but destroyed save for pieces of rim here and there. The two craters further west from the terminator from south to north are Manzinus (98 km.) and Mutus (78 km.). Craters B and A, both about 16 km. in size, can be seen on the floor of Mutus.
As a target the moon proved to be a very enjoyable subject on this evening of observation and sketching.

Sketching:

For this sketch I used: black Strathmore 400 Artagain paper 10”x 8.5”, white and black Conte’ pastel pencils and a blending stump. After scanning, Brightness was decreased (-2) and contrast increased (+2) using Microsoft Office Picture Manager.

Telescope: 10 inch f/ 5.7 Dobsonian and 9 mm eyepiece 161x
Date: 9-18-2008, 4:05 – 5:30 UT
Temperature: 15° C (60° F)
clear, calm
Seeing: Antoniadi III
Colongitude 129.5 °
Lunation 18.4 days
Illumination 90 %

Frank McCabe

Bullialdus and A and B
Sketch and details by Richard Handy

Sitting in replendent isolation on the lava plains of Mare Nubium, the magnificent 61 km Bullialdus reflects the early morning sunlight strongly off the steep cliffs ringing it’s western rim. If you were to stand on this precipice next to this face, a nervous downward gaze would reveal huge islands of collapsed rubble nearly 1800 meters of almost vertical drop below you. Wrapping around in great arcs with your field of view, on the opposite side of the crater, these giant terraces would appear as tumbled foothills rising from a deep gray plain, interrupted by the brightly lit jutting central peaks of Bullialdus. The wreath of folded crust that forms the glacis of Bullialdus is one of it’s most alluring aspects. It seems replete with craggy flows of broken crustal rock arranged radially around the outer rim. As an Eratosthenian aged crater, little is preserved of this iconic crater’s once prominent ray system, but at one time it must have been quite a sight, powdery rays splayed across the long cooled Nubium flows. But time, sunlight and micrometeorites fade everything. Craters like Bullialdus are classified as complex craters. The force of the impact of the original asteriod is strong enough to distort the surface downward a few kilometers. In response to this compression, the surface rebounds almost explosively, creating extraordinay results: central peaks and rim terrace mega collapse slides. Bullialdus’s peaks are close to 1000m high. The annulus of mass wasting, especially in a couple of areas to the south west of the floor do appear to almost encroach on the central peaks. To the south of Bullialdus is Bullialdus A. There seems to be a scooped depression that connects Bullialdus to it’s diminutive neighbor, as if the shock of A’s formation created a landslide off this section of the glacis of Bullialdus. Futher to the southwest Bullialdus B echos this odd terrain.

Sketch Details:

Date: 6-25-07 Start- 4:30 UT End- 6:00 UT
or: 6-24-07 21:30 to 23:00
Lunation: 10.05 days Phase: 61.1 deg Illumination: 74.2%
Lib. in Lat.= +5 deg 56 min Lib. in Long.= -00 deg 10 min
Seiing: Antoniadi II to III Weather: clear
Telescope: 12″ SCT f/10
Bino viewer: W.O. Bino-P with 1.6X nosepiece
Eyepieces: 12.4 mm Meade Super Plossls
Magnification: 393X
Medium: White and black Conte’ Crayon on textured black Strathmore paper.
Sketch size: 18″x 24″

Schluter, Grimaldi, and Riccioli Craters
Sketch and Details by Frank McCabe

At one day before full moon the illumination along the western terminator, nearly at the limb was highlighting the Upper-Imbrium crater Schluter (92 km.) with its central peak protruding out from the darkness of the crater floor. The outer reaches of Mare Orientale in the name of the Cordillera mountains were just beyond the sunlight at the lunar limb. The largest feature in this sketch is the lava covered, very dark floored impact basin known as Grimaldi (230 km.) What we see of Grimaldi is the inner ring of a 440 kilometer, two ringed mini-basin. This Pre-Nectarian impact event was originally described as a walled plain crater of advanced age with a heavily worn and battered rim. The basin is noted for a large gravitation anomaly beneath the surface associated with a high mass density concentration. Adjacent to Grimaldi to the west is semi-dark floored walled plain crater Riccioli (150 km.) At the same age as its eastern partner it shows damage and age especially from the ejecta pitched out by the Mare Orientale event.

Sketching:

For this sketch I used: black Strathmore 400 Artagain paper 9”x12”, white and black Conte’ pastel pencils and a blending stump. After scanning, Brightness was decreased (-5) and contrast increased (+4) using Microsoft Office Picture Manager.

Telescope: 10 inch f/ 5.7 Dobsonian and 9 mm eyepiece 161 x
Date: 8-16-2008, 3:15-4:40 UT
Temperature: 15° C (59° F)
Clear, calm
Seeing: Antoniadi III
Colongitude 85.7 °
Lunation 14.7 days
Illumination 99.4 %

Frank McCabe