Rupes Recta

Rupes Recta (latin for straight cliff) is a huge fault line or escarpment on the surface of the Moon, which can be seen just after daybreak at it’s Lunar location, when the Moon is about 8 days through its twenty-eight day cycle (around First Quarter Moon).

It is a dark and almost straight line,  stretching across the large crater which is almost dead centre of the above image.

The low angle of sunlight casts a shadow that gives it the appearance of a steep cliff, which is 240–300 m high, although it may not be as steep as it looks, because it is 2-3 km wide.

Its length is roughly 110 km and it is located in the south-eastern part of the Mare Nubium. The 17 km diameter crater Birt is adjacent, also Alpetragius and Thebit.

201190611 Rupes Recta crop
2019-06-11 Rupes Recta cropped and sharpened

I first spotted this object on 23rd May 2018, during a world record attempt for the most people stargazing across multiple locations across Australia. (For some odd reason observing the Moon is regarded as “Stargazing” by Guinness World Records, who over a year later have yet to publish the details of the new record we set that night).

I found myself staring at this straight line for the entire duration of the record attempt and wondering what the hell it was!

I didn’t spot it again until last night, when I was messing around taking some Moon videos – and there it was once more.

These images are from a magnified screen shot of the region, thus lacking quality.

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Exposure:  screen shot of zoomed video, in SharpCap.
Date:  2019-06-11.
Moon: 8 days since New Moon.
Location:  Outer suburban.
Conditions:  Clear.
Location on the Moon: 22.1°S 7.8°W.


Image acquisition software:  SharpCap, live stacked.
Image post-processing:  GIMP.
Cropping:   no.


Telescope: SkyWatcher Esprit  Type: 120ED triplet refractor
Focal: 840 mm F/7 Mount: SkyWatcher EQ6-R Pro
Camera: ZWO ASI 071 MC Pro Type: CMOS 28.4mm 16 Mpx
Optical aids: Flattener: Y; filter: N Guiding: No
Polar aligning: QHYCCD PoleMaster Polar Error: 03’ 50”


Image © Roger Powell



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