No access to Gruithuisen's "Lunar City"

[Nyctimene]

Yesterday evening I tried to spot this feature, located in Sinus Aestuum, with my 8" f/4, using a favourable illumination close to the terminator. The "Wallwerk", seen by Gruithuisen with a 2.4" Fraunhofer at 90x mag almost exactly 200 years ago (July 12th, 1822) is located N of the crater Schroeter (between Schroeter W/A and Schroeter T). It's described as a "herringbone" pattern, with rows of hills "branching out like the veins of a leaf from the midrib" at an angle of 45°. Rükl's map No 32 shows it quite well; in Wood/Collins's "21st Century Atlas of the Moon", chart 17, it is hidden by the label "Aestuum Pyroclastics". With mag 133x, I could just make out the double crater Schroeter W/A, but, due to the bad seeing, neither Schroeter T nor further details. The seeing left even other features invisible, e.g. Thebit D at the N end of Rupes Recta, and Catena Davy. So I finished the observation after 45 min at 21.00 CEST. I'll wait for better seeing conditions and give it another try.

Has anybody observed this region, and what were the impressions?

Here's some additional information from the CloudyNights forum, including Gruithuisen's drawing. (N.B.: Carol's photography (comment No.5) sees to be left-right mirrored, contrary to the given compass directions; and comment 12+13)

https://www.cloudynights.com/topic/85504-gruithuisens-lunar-city/

Thanks for reading

Stephan

 

 

[Nyctimene]

Was successful  this evening to spot this elusive structure with the mighty Skywatcher Heritage 130 P Flextube under slightly better seeing conditions. With the root point at Schroeter T, a N-S-line extended to Schroeter W/A, the "herringbone"  or "leaf vein" pattern, with two or three straight brighter lines on each side at a 45° angle was faint but distinctly visible in moments of better seeing with 183x mag (Seben Zoom 8 mmf+2.25x Barlow). The branching lines appeared straight and somehow artificial, resembling a child's first drawings of a tree with branches. The "Wallwerk" is small (approximately the diameter of Eratosthenes close by - 60 km) and faint, but the Heritage showed once more it's capabilities. Very pleased with the success.

Stephan

Edited May 9, 2022 by Nyctimene

[Bill Harris]

This is an interesting area, being located in one of the lunar dark spots with a history of effusive volcanic activity.

I'll be following this thread, and have started another marker thread over at Cloudy Nights:

https://www.cloudynights.com/topic/827539-gruithuisens-lunar-city-resuscitated/

Edited June 12, 2022 by Bill Harris