During the Covid pandemic, I got back into amateur astronomy after a long absence that dated to around the time I started graduate school. It was an activity that didn't involve going out anywhere and could be pursued from home. More particularly, I came back to observing the Moon. For a long time it was more a nuisance than an object of interest, and I used to plan astronomy around the need to avoid its presence in the evening sky. But after 2020 it took on a new allure. Not only was there a much greater diversity of surface features than I ever appreciated in the past, but lunar observing presented another opportunity to push my current setup to its limits.
I started working through the "Lunar 100", a list of interesting lunar features curated by legendary observer and planetary scientist Chuck Wood. The list was introduced in a 2004 Sky & Telescope article as "an attempt to provide Moon lovers with something akin to what deep-sky observers enjoy with the Messier catalog: a selection of telescopic sights to ignite interest and enhance understanding." Wood's intent in assembling the list was to "challenge observers to find and observe them all and, more important, to consider what each feature tells us about lunar and Earth history."
I started working through the "Lunar 100", a list of interesting lunar features curated by legendary observer and planetary scientist Chuck Wood. The list was introduced in a 2004 Sky & Telescope article as "an attempt to provide Moon lovers with something akin to what deep-sky observers enjoy with the Messier catalog: a selection of telescopic sights to ignite interest and enhance understanding." Wood's intent in assembling the list was to "challenge observers to find and observe them all and, more important, to consider what each feature tells us about lunar and Earth history."
A few years after first encountering the Lunar 100, I'm still working through the list. (40 more features left to go!) Wood's encyclopedic knowledge of the Moon shines through in the selections on his list, which is organized in order (by his reckoning) of the least to most difficult to spot. But it's equally clear that he must have discarded some potential additions along the way, lest the entries run into the hundreds or more.
As I racked up more lunar observing hours, I started seeing interesting features not on the Lunar 100. So I started a list of my own as a kind of supplement to the Lunar 100. Some are previously known, while I find no record of certain others. And quite often the visibility of a particular feature may be so sensitive to the local altitude of the Sun above the lunar horizon that it lasts only a few hours. The main criterion for inclusion, beyond illustrating some interesting aspect of lunar geography, is that features must be visible from my 8-inch (20-cm) telescope under typical seeing conditions at my site. Given that I'm at a low elevation, my site is strongly seeing-limited with typical full-width at half-maximum (FHWM) values for stars on the order of 2-3 arcseconds. That's vastly higher than the diffraction limit for my telescope. On top of that, my fast Newtonian system has pretty bad uncorrected coma. Despite that, I can confidently locate objects on the Moon whose linear extent is around 2 kilometers. And I've spotted some rilles whose widths are on the order of a few hundred meters. (Shadows really help!)
The list below contains a basic set of information for all entries. The features are numbered in no particular order. A thumbnail image of each is provided; these are drawn either from my own images or those taken by the Lunar Reconnaissance Orbiter Camera (LROC) in orbit around the Moon. Coordinates are given in selenographic coordinates for cross-referencing on any lunar map. The "age" refers to the number of nights past new when the feature is best seen. My atlas of choice is Antonín Rükl's classic "Atlas of the Moon", so I cite the number of his atlas map on which the feature's location may be found. Lastly, I give a short description of the feature and its significance.
This list is meant to grow over time as I spot new and interesting features, and I will periodically update this page with new entries. It's also available as a CSV here. If readers spot any errors, or have any interesting features not on the list to suggest for addition, please contact me.
As I racked up more lunar observing hours, I started seeing interesting features not on the Lunar 100. So I started a list of my own as a kind of supplement to the Lunar 100. Some are previously known, while I find no record of certain others. And quite often the visibility of a particular feature may be so sensitive to the local altitude of the Sun above the lunar horizon that it lasts only a few hours. The main criterion for inclusion, beyond illustrating some interesting aspect of lunar geography, is that features must be visible from my 8-inch (20-cm) telescope under typical seeing conditions at my site. Given that I'm at a low elevation, my site is strongly seeing-limited with typical full-width at half-maximum (FHWM) values for stars on the order of 2-3 arcseconds. That's vastly higher than the diffraction limit for my telescope. On top of that, my fast Newtonian system has pretty bad uncorrected coma. Despite that, I can confidently locate objects on the Moon whose linear extent is around 2 kilometers. And I've spotted some rilles whose widths are on the order of a few hundred meters. (Shadows really help!)
The list below contains a basic set of information for all entries. The features are numbered in no particular order. A thumbnail image of each is provided; these are drawn either from my own images or those taken by the Lunar Reconnaissance Orbiter Camera (LROC) in orbit around the Moon. Coordinates are given in selenographic coordinates for cross-referencing on any lunar map. The "age" refers to the number of nights past new when the feature is best seen. My atlas of choice is Antonín Rükl's classic "Atlas of the Moon", so I cite the number of his atlas map on which the feature's location may be found. Lastly, I give a short description of the feature and its significance.
This list is meant to grow over time as I spot new and interesting features, and I will periodically update this page with new entries. It's also available as a CSV here. If readers spot any errors, or have any interesting features not on the list to suggest for addition, please contact me.
Map showing the locations of the features on the "Beyond the Lunar 100" list with numbered markers.
Barentine's List ("Beyond the Lunar 100")
| A | B | C | D | E | F | G | H | I | |
|---|---|---|---|---|---|---|---|---|---|
1 | B | Image | Feature Name | Lat. | Long. | Size (km) | Age (days) | Rükl Chart | Description |
2 | 1 |  | Hayn massif shadow | 63.3ºN | 82.4ºE | ? | 13 | 6 | A lunar "clair-obscur", a type of ephemeral feature resulting from the interplay of light and shadow |
3 | 2 |  | Rheita E | 34.2°S | 48.9°E | 68 | 4/18 | 68 | An odd and highly elongated crater that may have resulted from the impact of three co-orbital objects in rapid succession |
4 | 3 |  | The Gardner 'megadome' | 16.2ºN | 34.0ºE | 60 | 5 | 25 | A massive, 70-km-wide possible intrusive dome in northern Mare Tranquilitatis |
5 | 4 |  | Mons Maraldi | 20.3°N | 35.3°E | 16 | 5 | 25 | A probable extrusive volcanic mound |
6 | 5 |  | Cassini's bright spot | 32.8ºS | 4.4ºW | n/a | 8-22 | 65 | Unusually bright patch of highlands that has perhaps the highest albedo of any location on the lunar nearside |
7 | 6 |  | Alpetragius | 16.0°S | 4.5°W | 40 | 8/22 | 55 | Complex crater with a pronounced central peak dubbed the "egg in a nest" by Gerard Kuiper |
8 | 7 |  | The "Wallwerk" | 5.7ºN | 7.9ºW | ~50 | 8/22 | 32 | Series of nearly parallel ridges in a region of unusally low albedo that was once mistaken for a city |
9 | 8 |  | Dembowski Mensa | 2.1ºN | 8.2ºE | ~25 | 7/21 | 34 | Good example of a "mensa", or mesa-like plateau whose origin is not fully understood |
10 | 9 |  | Birt domes and Rima Birt | 20.5ºS | 9.8ºW | ~5 | 7/21 | 54 | Excellent example of effusive lunar domes and an associated rille beginning at the summit cleft of one of the domes |
11 | 10 |  | The lunar "Cookie Monster" | 39.5°S | 17.7°W | 64 | 8/22 | 64 | Chance arrangement of craters centered on Heinsius that under certain Sun angles looks like Cookie Monster's face |
12 | 11 |  | Mons Moro | 11.8°S | 19.8°W | 10 | 9/23 | 42 | Dark, isolated mountains of uncertain origin |
13 | 12 |  | Marth | 31.1°S | 29.3°W | 7 | 10/24 | 63 | Concentric-ring crater in Palus Epidemiarum |
14 | 13 |  | The "Helmet" | 16.8ºS | 31.5ºW | 55 | 10/24 | 52 | A ultraviolet-absorbing "red spot" with high optical albedo located within the Procellarum KREEP terrane, a part of the lunar crust that formed relatively late in the Moon's history |
15 | 14 |  | Vitello | 30.4°S | 37.5°W | 42 | 11.24 | 62 | Circular fractures across a crater floor surrounding the central peak |
16 | 15 |  | Doppelmayer | 28.5°S | 41.4°W | 64 | 11/24 | 52 | Circular fractures across a crater floor surrounding the central peak, which rises almost as high as the crater's rim |
17 | 16 |  | Mons Hansteen | 12.1°S | 50.0°W | 30 | 12/26 | 40 | An extrusive volcanic mound that may be the only such example gound outside of a mare context |
18 | 17 |  | Zupus massif | 17.1°S | 51.7°W | 25 | 12/26 | 51 | 1800-meter-tall mountain that casts a considerable shadow at low Sun angles |
19 | 18 |  | Lamarck massif | 22.1ºS | 67.4ºW | ~10 | 12/26 | 50 | 3000-meter-tall mountain that casts a considerable shadow at low Sun angles |
20 | 19 |  | Miyamori Valley | 1.3ºS | 70.3ºW | ~25 | 14 | 39 | A clair-obscur located roughly between the crater Riccioli and Lohrmann that appears to be a valley but is actually the shadow from a linear ridge seen at certain librations |
21 | 20 |  | Schiller-Zucchius basin | 56.0°S | 45.0°W | 325 | 11/25 | 71 | An ancient (pre-Nectarian) peak-ring basin, one of the oldest known on the Moon |
22 | 21 |  | Mons Herodotus | 27.5°N | 52.9°W | 7 | 11/25 | 18 | Bright, isolated mountain peak on the Aristarchus Plateau also known as "Star-Tip Mountain" because of its bright, point-like appearance around local sunrise |
23 | 22 |  | Mairan T | 41.8°N | 48.1°W | 6 | 11/25 | 9 | A silicic volcano with a summit crater likely resulting from the collapse of its magma chamber |
24 | 23 |  | Wolf | 22.7°S | 16.6°W | 26 | 8/23 | 54 | Likely a collapsed felsic volcanic caldera active as recently as 1.7 billion years ago |
25 | 24 |  | Cinder cone near near Lassell D and Lassell J | 15.0°S | 10.9°W | 3 | 14-16 | 54 | An isolated cinder cone on Mare Nubium best seen as a dark spot around full Moon |
26 | 25 |  | The Hesiodus Ray | 29.5°S | 15.6°W | -- | 8/23 | 54 | A beam of light seen briefly at local sunrise/sunset across the floor of craters Hesiodus/Pitatus resulting from a breach in the wall separating them |
27 | 26 |  | Alhazen ɑ | 20.0°N | 69.7°E | -- | 17 | 27 | Mountain peak on the eastern edge of Mare Crisium with a distinctly streaked appearance |
28 | 27 |  | "Eimmart K Mountains" | 18.3°N | 67.07°E | 50 | 17 | 27 | Small cluster of mountain peaks in eastern Mare Crisium exemplifying lunar kipukas (islands of older land surrounded by younger lava flows) |
29 | 28 |  | The "Lunar N" | 32.2°S | 32.0°W | 30 | 10/24 | 63 | Complex pattern of rilles near the crater Ramsden resembling a capital letter "N" at low Sun angles |
30 | 29 |  | The "Darwin Diamond" | 19.4°S | 69.5°W | 20 | 13 | 50 | A flat-topped rise in the western half of the crater Darwin that looks like a near-perfect quadrilateral under specific lighting conditions |