Rupes Recta on the Moon

Rupes Recta, "The Straight Wall", a linear fault - March 15, 2008
Rupes Recta, “The Straight Wall”, a linear fault – March 15, 2008

Object Name: Rupes Recta on the Moon
Object Type: Moon crater
Location: Chiba Japan
Date: 2008/3/15
Media Black graphite pencil on a white paper. Contrast adjusted with PC.

Equipments:: Telescope: Televue 85, Eyepiece: Pentax XW-10 with Power mate 2.5x

After outlining major features using solid lines, dotted lines and numbers(1-9) are used to express gradation in brightness(right). The numbers are replaced with “real” darkness after the lines are copied on another paper (left).



Aristarchus, Prinz and the Harbinger Mtns.

Aristarchus, Prinz and the Harbinger Mountains-June 20, 2013
Aristarchus, Prinz and the Harbinger Mountains Region-June 20, 2013

The kilometer high rim of Prinz (47 km.) crater was casting a shadow across its own lava flooded floor. The uplifted Harbinger mountains were also casting fine shadows in this region of the lunar surface with its large magma ponds pushing up and freezing in the distant past. The uplifting doming in the region created many fissures for lava escape and flooding to occur. The fissures can be seen clearly on nights of steading seeing. I was denied that detailed view on this night. From the crater Krieger (22 km.) north and somewhat east of Aristarchus (40 km.) four distinct long shadows could be seen crossing to the 70 km. fault called Toscanelli at the edge of the Aristarchus plateau where the terminator was located during the rendering of this sketch.
A fine view in any telescope.

For this sketch I used: black Canson paper, white and black Conte’
pastel pencils and blending stumps, white Pearl eraser
Telescope: 10 inch f/ 5.7 Dobsonian and 9 mm eyepiece 161x
Date: 06-20-2013, 02:40 – 04:10 UT
Temperature: 19° C (68° F)
Partly cloudy, hazy
Seeing: Antoniadi IV (poor)
Frank McCabe

Rupes Recta and Thebit

Rupes Recta and Thebit
Rupes Recta and Thebit


I send to you a sketch created last year of a favorite region of the lunar landscape. Rupes Recta, latin for “Straight Fault” or “Straight Wall” is a lunar fault at the southeastern region of Mare Nubium. This sketch was created at ~8 days lunation when the angle of the Suns light casts deep shadows across the linear fault giving it the appearance of a very steep cliff.

In spite of appearances, Rupes Recta is not a sheer cliff, though still relatively steep. It rises above the mare plain ~250 to 300 meters high with ~20 degree grade as reported by some authors. The fault runs NW to SE for ~120 km terminating at the south end as a jumble of rubble and then a smooth curved wall. This creates the appearance of a sword as likened by 17th century Huygens, the curved region being the sword handle with the cliff edge being the sword blade.

Seeing was very good on this night but the angle of light at the terminator did not illuminate the “handle” as well as on other nights of observing. When this region is observed days later the steepness of the fault vanishes and appears as a step transition instead. The light plays amazing tricks on the eye.

Sketched in relief to the west of the fault is crater Birt just becoming lit. Thebit and Thebit A are sketched to the SE of Rupes Recta.

Cindy (Thia) Krach
Maui, Hawaii
4,000 el.
12.5” Portaball
14mm 109x, 9mm 169x

Rupes Recta at Sunrise

Rupes Recta
Rupes Recta

I set up to sketch Rupes Recta on the floor of Mare Nubium. From the eastern edge of Mare Nubium you can see the triplet craters, Thebit (57 km), A and L. Next moving westward is the Imbrian escarpment Rupes Recta , not a true wall in the usual sense but on one side standing more than 300 meters high at some locations and 114 km in length. The scarp face would be visible from the rim of young crater Birt’s (17 km) to the west of “straight wall” if you could get there. Touching the rim of Birt to the east is Birt A.

For this sketch I used: black Canson paper (8” x 10”), white and black pastel pencils, assorted erasers, and blending stumps

Telescope: 13.1” f/6 Dobsonian working at 222X (9mm ocular)
Date: 11-22-2012 01:00-02:45 UT Temperature: 12°C (54°F)
Hazy, slightly breezy
Seeing: Antoniadi III
Colongitude 10.1 °
Lunation 8.1 days
Illumination 64.9%
Alt. 45°

Frank McCabe

Ancient Thebit and Rupes Recta

Rupes Recta

Ancient Thebit, Rupes Recta, Thebit, Birt, Promontorium Taenarium
Move mouse over image to view labels.

Object Name: Ancient Thebit, Rupes Recta, Thebit, Birt, Promontorium Taenarium
Object Type: Lunar crater, lunar graben, lunar dorsum.
Location: York, UK
Date: 3rd December 2011
Media: graphite pencil, white paper

The straight wall, or Rupes Recta, is the best example of a simple fault on the moon, and visible even with a small scope. It’s 300m high and 114km long. It lies radial to the Mare Imbrium impact basin, in line with a lot of nearby sculpture from that event, but that is probably just coincidental. It also lies in line with the edge of the Mare Nubium basin and cuts across the floor of an ancient crater lying across the edge of that basin, known as Ancient Thebit, whose eastern edge marks the edge of Mare Nubium and western edge is marked by wrinkle ridges in the mare. Rupes Recta marks where the edge of Mare Nubium would have been if Ancient Thebit had never formed. The sequence of events is therefore likely to have been:

1. Nubium impact occurs, forming Nubium basin (4.55-3.92 billion years ago).

2. Ancient Thebit impactor hits edge of Nubium Basin.

3. Nubium basin floods with lava forming Mare Nubium (approx 3.3 billion years ago according to crater counts), flooding Ancient Thebit.

4. Nubium basin slumps in the centre, forming Rupes Recta along its former edge.

I failed to see Rima Birt, a lava rille that travels from a dome on the northern border of ancient Thebit to crater Birt. However, seeing was not good. I did nonetheless make out the dome that marks its origin, which I had not seen before.

Rimae Run Through It

Object Name: Petavius
Object Type: Lunar Crater
Location: Bristol, UK
Date: 24th Oct 2010
Media (graphite pencil sketch at the scope and then digitized using graphics tablet and Photoshop)
I usually sketch in some detail at the scope (mainly HB and 2B). I then scanned the result into Photoshop and used a Bamboo Pen graphics tablet to remaster the sketch. The final sketch was then “blurred” a touch to simulate the actual view which is never as sharp as I would like to see!)

Observational data: I use a Nexstar 8SE teamed with a Hyperion 8-24 mm zoom. Most of the sketch was at the 8mm stop and was drawn in good seeing conditions. The moon was 17 days old. I could see the circular crater formation of Petavius situated on the South bank of Mare Fecunditatis. The steep slope was rugged and contained a few craterlets. Wrottersley could be seen in the North-West (with a central peak) while Hase and Snellius could also be seen in the South. The main feature was the central mountain inside Petavius and the Rimae that ran from this to the crater wall. Very distinctive at the angle observed. Otherwise the floor was pretty flat. To the north I could see lines running way from the crater rim. The shadow obscured most the the craters to the East.
Hope you enjoy,

Clear Skies

Chris Lee

Rim of Nectar

Rim of Mare Nectaris

Rim of Mare Nectaris,
with craters Theophilus, Cyrillus and Catharina, and Rupes Altai

Sketch and Details by Peter Mayhew
Hover mouse over image to view labels.

The sketch was made with graphite pencil on white paper at the eyepiece. My instrument is a Skywatcher Skyliner 152mm f8 Dobsonian, and I used a 10mm eyepiece and x2 Barlow. The moon was day 19-20. The sketch took about one hour, during which time I had to reposition the scope about 100 times as the earth’s rotation took the target out of view. The famous trio of craters, Theophilus, Cyrillus and Catharina lie on the edge of the Nectaris impact basin. Theophilus is the youngest crater of the three, an estimated billion years old with a large central peak with multiple summits, 1500m high. It has an impressive terraced rim. Cyrillus is much older (3.5-3.8 billion), and retains a central peak too, unlike Catharina to its north. To give a sense of scale the latter is 104km across. The landscape all around is dominated by the Rupes Altai, a scarp 1000m high and 500km long. This marks the ripples in the crust formed by the Nectaris impact. Mons Penck (4000m high) forms part of its northern extent. Low ridges and hills throughout the region are aligned with the impact, nearly 4 billion years ago. Three fruity craters and a fascinating reminder of the moon’s dramatic past.

The Great Peninsula and Adjacent Sea

The Great Peninsula and Adjacent Sea

The Great Peninsula and Adjacent Sea
Sketch and Details by Frank McCabe

On this cold early morning I chose for sketching the lunar highland region that is pointed directly to Earth, namely the Great Peninsula and the adjacent Mare Nubium. It would be much fun to draw the entire visible part of the Peninsula in just one sketching session at the eyepiece but that is just a dream with the terminator features changing so quickly. I focused on just what I could handle inside my self-imposed two hour limit. The seeing was good and that alone means ignoring some visible detail within the allotted time.
I was well into the sketch when I noticed my first mistake. I was using the excellent black Canson acid-free paper and one edge was embossed with the words “Colorline Canson…” which I discovered about one hour into the sketch as I began drawing over these words… Dah.
The terminator was cutting across the western part of the peninsula which was diagonal and inverted in the eyepiece from upper right to lower left in the Newtonian telescope.
From top center to lower left the large ancient craters with floors in full darkness are: Regiomontanus (125km.) with an illuminated, cratered peak somewhat off center; Purbach (120km.) with its arching central peaks picking up the last rays of sunlight; Smaller Thebit (60km.) closest to Rupes Recta (Straight Wall); Arzachel (100km.) with all but the rim in total darkness (note: that was not the case before I started sketching); and lastly Alpetragius( 40km.) with the tip of its huge central peak catching light.
The two smallish and younger craters on the other side of Rupes Recta are Birt (17km.) and Nicollet (15km.). With such good seeing many smaller craters were clearly visible across the Sea of Clouds. While observing this region after finishing the sketch in twilight, clouds moved in and closed out any further viewing.
Sketching is always a series of compromises, if you want the moon high in the sky this time of year you are limited to the early morning. During the fall early morning is the coldest part of the day and you need to give up some sleep time.
It was an adrenalin rush to see the moon on this morning and enough to keep warm.


For this sketch I used: black Canson paper 9”x 13”, white and black Conte’
pastel pencils , and Conte’ crayons, a blending stump, plastic eraser.
Telescope: 10 inch f/ 5.7 Dobsonian with 6mm (241x) eyepiece
Date: 10-11-2009 9:30-11:30 UT
Temperature: -3°C (27°F)
Clear becoming mostly cloudy, calm
Seeing: Antoniadi II and briefly I
Co longitude 182°
Lunation 22.7 days
Illumination 49.4%

Oak Forest, Illinois

Frank McCabe

A Rupes and a Rima

Rupes Recta

Rupes Recta and Rima Birt
Sketch and Details by Balázs Benei


This is my other sketch, I made it at the beginning of April. Rupes Recta was very easy to observe, it was totally in the field of vision. Rimae Birt was not so easy but I could see it firmly. The seeing was very good at times, I could observ the crater Birt D, which had only 3km (~2miles) diameter. I think this was the end of the definition of my telescope. I made the sketch with graphite pencil.

My equipment: 110/800 (4′) Newtonian reflector, 2x barlow, 10mm eyepiece, 160x magnification.

Yours sincerely
Balázs Benei

Object name: Rupes Recta, Rimae Birt

Object type: Lunar rille, Lunar rimae

Location: Gyöngyös, Hungary

Date: 2009. 04. 04. 17:35 – 18:55 UT