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.
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.
Exposure: screen shot of zoomed video, in SharpCap.
Moon: 8 days since New Moon.
Location: Outer suburban.
Location on the Moon: 22.1°S 7.8°W.
Image acquisition software: SharpCap, live stacked.
Image post-processing: GIMP.
|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