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'The Miyamori Valley' between Riccioli and Lohrmann


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I was observing the Moon last evening with my Celestron C90 Mak. Along the terminator at the lunar equator, a dark straight line nearly at right angles to the terminator between craters Riccioli and Lohrmann was visible. I set up my 8 inch SCT and oberved the line visually and captured the image below. It seemed to extend across Riccioli but this could have been a trick of the light. I did a bit of research and discovered that this feature is unofficially named 'The Miyamori Valley'.
Thanks for looking,

Clear skies




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I saw this feature yesterday too, it  was showing very well and looked like a valley. I was wondering what it is, as it did not show  on my maps. The LROC map suggests it's a  boundary between high and low terrain. Thanks for idenitifying it! There seems to be  a long history of this feature since its discovery 200 years ago.

Edited by Nik271
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I too was intrigued by this feature. I observed it at low power, but when I increased the magnification to try and figure out what it was it seemed to break up into a series of distinct shadows. I was experimenting with Binoviewers and eyepiece combinations and didn't feel I was able to do the feature justice.

Very interesting to know what it actually is. Thanks for posting @Peter_D


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2 hours ago, Nik271 said:

I managed to get this image from the LROC map. it shows some kind of trench between Roccioli G and Lohmann B:


I can see how that might look continuous at lower powers and potentially break up a bit under more magnification. Interesting picture thanks.


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  • 11 months later...

Spotted the "Miyamori Valley", unintended, yesterday evening, during revisiting the Grimaldi/Lohrmann/Riccioli/Hevelius region with the 5.1" Heritage. At 19.00 UT, the Colongitude was 71.2,  Libration in Longitude -4.1°, and Riccioli's crater rim just beginning to brighten. At 130x-150x mag, and moderate seeing, the "valley" presented as a deep black triangle, narrow based, starting from the W flank of Lohrmann and extending, tapered, to the W, with a tiny bright spot in the middle of the triangle (the valley way more distinct than shown in the photographs above, where Riccioli is fully illuminated). I'd guess, that it's an easier catch, when you try to spot it, before Riccioli gets illuminated. A nice addition to my collection of peculiar moon formations; many details can be found in the "Luna Cognita" handbook, 18-17.

Thanks for reading


Edited by Nyctimene
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  • 2 weeks later...

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