Category: terrae

Rosenberger and Vlacq near the Terminator
By Frank McCabe

  
  This region of the moon is often called the confusing southeastern lunar highlands
for all the large and medium sized look-alike craters. This appearance continues
to the lunar far side as can be see in lunar orbiter photos. But looking again the
picture really changes dramatically at low sun.  The two large craters I have
chosen for this sketch are both ancient (pre-Nectarian) and pre-date the early
basin formation on the moon. Rosenberger crater (96 km.) is the largest of the
pair to the left (east) in the drawing. This four billion year old crater has a
rim worn down to the level of the surrounding highlands by numerous crater impacts
and inner wall subsidence that has obliterated most of the wall terracing. It is
2.6 kilometers from the highest rim point to the mostly flat crater floor which in
the low sun was showing off its low central peak. A crater of 14 km. was about to
be consumed by shadow at the time of this sketch. This floor crater is Rosenberger
S. The other large crater to the southwest of Rosenberger is Vlacq, a crater of 89
kilometers and from all appearances perhaps the youngest of the pair. The twin
peaked central mountains and terraced walls give this crater a younger look. It
also appears from the bulging of the wall shared with its larger neighbor that the
body that struck the moon forming Vlacq came in second.               
  The observing and sketching was enhanced by steady seeing intervals that lasted
several minutes at a time.
  
  Sketching:

For this sketch I used: black Strathmore 400 Artagain paper, 9”x 10”, 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: 11-28-2007 5:30-7:00 UT
Temperature: -3°C (26°F)
partly cloudy, breezy
Seeing: back and forth between Antoniadi II and III
Co longitude: 135.2°
Lunation: 18.5 days
Illumination: 80.3 %

Messala and environs
By Frank McCabe

Clear windless sky during the day and at night with temperatures just above the
freezing point of water, these are ideal weather conditions in winter for the
Midwestern USA. The waning gibbous moon was bright and high at midnight following
Mars across the celestial hemisphere. Through my 10” telescope I zeroed in on the
region north of Mare Crisium. I then turned on the drive platform and began
sketching the region of the terminator centered on ancient pre-Nectarian age
crater Messala (126 km.). This walled plain crater in the waning sunlight was
showing off its rubble covered irregular floor and battered walls. Although the
seeing was not the best, which stopped me from sketching Mars, this region of the
lunar northwest was putting on a good show. The floor in addition to being lava
covered, irregular and dark, appears slightly convex or domed. To the southwest
large much younger crater Geminus ( 88 km.) with its central peak just beyond the
shadowed floor was showing
 its greater depth and terraced walls. Bernoulli (50 km.) closer to the terminator
is filled with shadow too. Touching Messala to the north is Schumacher (63 km.)
with its dark smooth floor and beyond the apron of this crater northward is ancient
Lacus Temporis (Lake of Time). To the southwest of Lacus Temporis are the ancient
craters Shuckburgh (41 km.) and then Hooke (37 km.).
  
  Sketching:

For this sketch I used: black Strathmore 400 Artagain paper, 12”x 9”, white and
black Conte’pastel pencils and a blending stump. Brightness was slightly decreased
after scanning.

Telescope: 10 inch f/5.7 Dobsonian and 9mm eyepiece 161x
Date: 12-26-2007 5:30-7:00 UT
Temperature: 0°C (32°F)
 clear, calm
Seeing: Antoniadi III
Co longitude: 113.7°
Lunation: 16.6 days
Illumination: 93.3 %

  Just two days past full moon, floor fractured crater Furnerius (125 km.) was well
placed relative to the sunset terminator to show off its interesting features.
This crater is one of the four large walled plain craters along the 60° E.
longitude line. Furnerius is the southern most of the four and placed not far from
the southeastern lunar limb. The other three which were visible at the eyepiece
from south to north but not sketched here are Petavius, Vendelinus and Langrenus.
Crater Furnerius is a pre-Nectarian crater and thus very ancient. It predates the
formation of the Nectaris basin. Basin debris and secondary impacts are scattered
across the floor and rim of this old battered crater. On the north side of the
crater floor a rille of 50 kilometers called Rima Furnerius can be seen. It
crosses the floor to the southeast and climbs the inner crater rim. Darker
smoother lava flooded areas can be seen on parts of the crater floor between the
rubble strewn regions created
 by the basin impact. Inner wall terraces and central peaks are completely absent
from this crater but large crater Furnerius B(22 km.) is clearly visible on the
floor. On the glacis of this crater to the north a bright young 12 km. crater
called Fernerius A can be viewed in line with Rima Furnerius. To the northwest a 75
km. Copernican era crater Stevinus, stands impressively with its sharp rim, central
mountain peak and low hills. South of Furnerius a smaller yet equally ancient
crater Fraunhofer (57 km.) was showing a dark flat half shadowed floor. On the
northwestern rim of this crater Fraunhofer V (24 km.) could be identified by a
small sliver of light striking its inner southeast rim.
  
  Sketching:
  
  For this sketch I used: black Strathmore 400 Artagain paper, 9”x12”, 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: 10-28-2007 6:05-7:45 UT
  Temperature: 0.7°C (33°F)
  Clear, calm
  Seeing:  Antoniadi III- IV mostly poor
  Co longitude: 115.4°
  Lunation:  17 days
  Illumination:  93.7 %
  
  Frank McCabe

Craters Clavius and Blancanus
  
  Among the large craters of the lunar southern highlands, two nearly 4 billions old
impacts stood out on this morning before my  local sunrise. These craters are 225
km.diameter Clavius and smaller 109 km. Blancanus. Clavius is not only old and
large but is blanketed with numerous craters and craterlets. At the center of this
large crater are the reduced remains of once regal central peaks. The atmosphere
was steady enough to pick out cratelets less than 1.5 km in diameter during
periods of excellent seeing. Crater Clavius is famous for its semicircular crater
sequence of decreasing size beginning with 49 km. Rutherfurd at the inner
southeastern wall and continuing with 27km. D, 20 km. C, 12 km N, 11.3 km J and
7.5 km JA. The north-northeastern rim of Clavius has a large crater resting it.
This 52 km. diameter crater is Porter. A broad crater ray was clearly visible
crossing the floor of Clavius just to the west of Porter and Clavius C. Much of
the floor of crater Clavius
 remains smooth which implies the flow of melted rock in the past. Some geologists
speculate it is from the ejecta of the Orientale basin. Some small secondary crater
chains point back in that direction.
  
  Sketching:
  For this sketch I used: black Strathmore 400 Artagain paper, 9”x12”,  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: 9-2-2007 8:15-9:25 UT
  Temperature: 17°C (62°F)
  Clear, calm
  Seeing:  Antoniadi II-III
  Co longitude: 53.9°
  Lunation:  20.39 days
  Illumination:  70 %
  
  Frank McCabe

Distinctive crater Stofler resides in the midst of the dense and chaotic crater field of the southern hemisphere of the Moon. One clear but very chilly evening in January 2007, the challenge of trying to capture the view was more than I could resist – this is my attempt. The sketch was carried out using white and black Conte’ pencils and chalk pastels on black ‘Canford’ paper. I began by marking out the main crater shapes using white Conte’ pencil, then I used a small chunk of white chalk pastel, broadside, to lay down the mare regions, blending this with a fingertip and a small cloth. More highlights were added (white Conte’ pencil), and a putty eraser used to define some of the features (and shadow extent) by negative drawing where I removed areas of pastel previously laid down. More detail was added with white Conte’ pencil as I went along, but there really was far too much to capture and I realized that I would have to quit while I was ahead and finish my outside drawing time before the view changed substantially. Once back inside I tidied up the sketch, removing the inevitable unwanted pastel smudges with a putty eraser, and re-defining some of the darkened inner crater edges with black Conte’ pencil, then using blending stumps (with touches of both white and black chalk pastel) to make final tiny adjustments. The sketch has been inverted and rotated in paint shop pro to give the standard orientation.

Sally Russell
 

Date: 25 January 2007

Time: 21.10-22.00 UT

Equipment: 105mm AstroPhysics APO/bino-viewer (mag x60)

Lunation: 7.3 days, 48.7% illumination

Sketch size: 6″ x 8″

The southern highlands of the Moon are almost completely dominated by craters in the 20 to 100 km size range, randomly scattered about the region. One way to determine relative ages of craters is to note which overlay or superpose over other craters or features, and the crater that obliterates or partially modifies another crater is usually younger. It is this principle that is the foundation of a stratigraphic approach to understanding lunar geological history. In the lunar highlands there is no shortage of overlapping or partially modified craters, and as Sally points out this region is about as densely chaotic as any on the Moon. A careful look at her beautiful sketch also reveals one of the great unsolved mysteries of the Moon. Many craters have smooth flat floors and the adjacent surface topography between these craters is also relatively smooth. The big question is: what is responsible for these smooth areas? Do the smooth floors and intercrater terrane reflect episodes of highland volcanism?  Or perhaps these areas are covered with thick layers of ejecta that settled out across the surface as a result of this large scale stochastical gardening.