Thursday, November 30, 2017


Last Tuesday evening at an Alpha Ridge impromptu, I decided to make it an exclusively Moon night, and not look at anything else.* Despite my reputation as a Lunatic, I hadn't done that a long time, and it felt good to get Back to Basics as regards lunar observing. I started out, as always, by putting in a relatively low power, 13mm Nagler eyepiece and taking in the Moon as a whole. Then I upped the magnification, moving to a 4.5mm Delos and cruising up and down the length of the terminator, looking for anything particularly eye catching.

Well, what really caught my eye was an intriguing line of three piercingly bright dots off to the right (in my mirror-imaged view) of the day/night line. They were almost starlike in their intensity and pointlike appearance, looking for all the world like a row of streetlights on a dark road. (See above image. The three dots just to the left of center were in  splendid isolation when I first caught sight of them.) I decided to stick with them and see what they would become (a mountain range? the wall of a crater? an escarpment?) as the sunrise overtook them. I first spotted them at about maybe 5:15 or so, and I ended up staying glued to that spot for a good three hours.

Changes occurred much more slowly than I had anticipated. While other features to the north and south of this mysterious line of dots rapidly revealed themselves as crater rims and gigantic peaks, the dots remained stubbornly unaltered as isolated points of light. They didn't merge together or expand in size, but rather multiplied in number. After maybe 20 minutes, there were four of them. then all of a sudden seven, as a tight little triangle of points popped out of the darkness all at once. It eventually became hard to keep track of how many there were, as a host of microdots gradually came on the scene. But for the longest time there wasn't even a hint of their ever joining up to form a recognizable landform.

Finally two set of dots merged into short arcs and the whole collection was assuming the appearance of a bow. I (entirely mistakenly) now assumed I was looking at a highly degraded rim of an ancient lava-flooded crater. And that's where things stood as the evening ended and I packed up to go home.

But that's not where the story ended. Once home, I shot out an e-mail detailing what I saw, and various club members responded with their ideas (a.k.a., guesses) as to the identity of the mysterious feature. It wasn't until Richard Orr sent me his image from Tuesday night (above) that a positive identification was made. I was observing the disconnected summits of an irregular line of hills just west of the crater Kunowsky. I went to Google Moon and turned on the Elevation feature. The feature jumped right out at me. It's also clearly visible in the chart by the incomparable selenographer, Antonin Rukl (right below this paragraph), centered at 36 degrees W, 2 degrees N. A photograph of the region can be seen here: , in which the feature appears right below and somewhat to the right of the crater Encke.

Unfortunately, whatever this landform is, it apparently has no name. At least, none that I can find. Richard noted that the dots were likely "small separate hills making the western boundary of Mare Insularum" but are not parts of a crater rim, nor of a mountain range. At this point, any speculations would be much appreciated!

* I didn't quite devote the entire evening to the Moon, since I began the session with a truly marvelous binocular view of Saturn and Mercury, both visible in a single field of view.

(Probably should have mentioned this earlier, but I was observing using a 90mm Stellarvue refractor on a Universal Astronomics Dwarfstar alt/az mount atop a Manfrotto tripod. No electronics whatsoever. I had to keep the object of interest centered by hand.)