Mare Imbrium

[David Levi]

I've just spent a pleasant hour observing the moon. In particular Mare Imbrium towards the terminator. There were two illuminated peaks beyond the terminator. One of them was a complex array of illuminated rock that I identified as the western edge of the Carpathian Mountains and the other one I estimated was not far off the Zirkel Ridge which would make it Mount La Hire.

Is there a term for these illuminated objects disconnected by darkness from the moon along the terminator? I've seen the word 'diamonds' used in a couple of reports referring to a string of lights. However the Carpathian Mountain peaks were not strung out in a line and so I was wondering if there was some other terminology in use. I've done a brief search of the Internet but nothing has popped out.

Some high cloud has just rolled in now.

[Relpet]

I can't answer your question but I was equally captivated tonight.  Only Mars and the Moon were visible between breaks in the cloud but the lunar clarity was 3D along the terminator.  Spell-binding.

[MartinHiggins]

Hi, I'm also observing from Cardiff and have been enjoying some really great lunar views this week. I've seen for the first time the phenomenon you describe through my new Celestron C8 and Williams binoviewers (previously using a MAK C90). Looking at Sinus Iridium I saw a floating peak just beyond the terminator which I think was Mont Pico . I happily admit to being gob smacked with the detail the C8 shows, especially those floating peaks. 

[David Levi]

That's an excellent setup you have there Martin @MartinHiggins. I've used the word 'floating' as well in the past. It describes the phenomenon quite well.

[Relpet]

4 hours ago, MartinHiggins said:

 I saw a floating peak.

Floating peaks!  A perfect description which I shall be delighted to borrow.  Many thanks.

[Paz]

I don't know if there is a proper word for bits being lit up that are isolated from the main lit body of the moon but I call them diamonds myself. These are one of my favourite things to look at and it is good fun to try and work out exactly what peak or rim you are looking at from the maps.

[Nyctimene]

Never came across a specific terminus for those isolated points of light in the shadowed parts of the moon. Btw., there is a "vice versa" phenomenon I've observed twice (Sept. 13th, 2016 and Apr. 4th, 2017)  at the Promontorium Laplace, the eastern border point of Sinus Iridum. I spotted a deep black tiny speck of shadow (presumed in a rift) far away from the terminator, surrounded by the gleaming bright floor of S. Iridum and Mare Imbrium; slowly getting smaller - rather spectacular; and , as it seems, another speciality of Sinus Iridum (besides the "Lunar buzz-saw" phenomenon and the "Golden Handle").

Stephan

[nebulaeman]

David:  The term I have always seen is "disconnected sunlit peaks!" However, this has typically been in my Grazing Occultation work where we have a disconnected sunlit peak along the Lunar Limb in our graze area that can effect the visibility of stellar events as we observe.  nebulaeman

[Astro Imp]

I enjoyed reading your report David. Lunar observing always gives us something new to view and enjoy. As to your question I don't know of a specific term for what you describe but it is certainly fascinating to see.