The Lunar 100, An Astronomer’s Guide

We astronomers love a good list of objects to find!

Perhaps the most classic of them all is Charles Messier’s eponymous catalog of deep-sky objects. We can strive to find all 110 Messier objects in a single night, or we can take many months (or years) to complete our study.

The Lunar 100 was created in the same vein – it’s a challenge for those of us that love to point our telescopes at the moon.

There are some major differences between the Messier catalog and the lunar 100 though, other than their subject matter. The Lunar 100 was deliberately designed to get harder as you work through it, it can not be successfully completed in one night, and it’s open to everyone on the planet, no matter where you live.

In this article, we’re going to explain exactly what the Lunar 100 is, share the complete list with you, and give you the essential guide to seeing each of the one hundred features on the list.

What is the Lunar 100?

The Lunar 100 list was Created by Charles A. Wood for Sky & Telescope Magazine in 2004. He is well known in astronomy circles for writing the great book ‘The Modern Moon: A personal View‘ (link opens Amazon in a different tab).

Check out our other favorite books about the moon.

What Charles set out to achieve was an education about the complexities of the lunar surface. His list does this not by showing, necessarily, the ‘best’ features the moon has to offer our telescopes but by showing the diversity of what’s available.

He arranged the hundred lunar features in rough order of difficulty. We begin with the moon itself, followed by earthshine – the light we see from the dark moon which is reflected from Earth – before moving on to actual features.

By the time we hit the final 20 discoveries, we’re looking for tiny craters, barely visible domes, views that can only be seen during lunar librations, and magnetic swirls in the regolith.

The whole point is to discover the moon in more depth, almost like receiving 100 lessons from a very knowledgeable teacher.

The Lunar 100 List

The whole lunar 100 list is reproduced below. You can download it as a PDF at the bottom of this page, where you’ll also find our comprehensive guide to finding the Lunar 100.

LFeatureSignificanceLat. (°)Long. (°)Diam. (km)
L1MoonLarge Satellite3.476
L2EarthshineTwice reflected sunlight
L3Mare/highland dichotomyTwo materials with distinct compositions
L4AppeninesImbrium basin rim18.9N3.7W70
L5CopernicusArchetypal large complex crater9.7N20.1W93
L6TychoLarge rayed crater with impact melts43.4S11.1W85
L7Altai ScarpNectaris basin rim24.3S22.6E425
L8Theophilus, Cyrillus, CatharinaCrater sequence illustrating stages of degradation13.2S24.0E
L9ClaviusLacks basin features despite its size58.8S14.1W225
L10Mare CrisiumMare contained in large circular basin18.0N59.0E540
L11AristarchusVery bright crater with dark bands on its walls23.7N47.4W40
L12ProclusOblique-impact rays16.1N46.8E28
L13GassendiFloor-fractured crater17.6S40.1W101
L14Sinus IridumVery large crater with missing rim45.0N32.0W260
L15Straight WallBest example of a lunar fault21.8S7.8W110
L16PetaviusCrater with domed and fractured floor25.1S60.4E177
L17Schroter’s ValleyGiant sinuous rille26.2N50.8W168
L18Mare Serenitatis dark edgesDistinct mare areas with different compositions17.8N23.0EN/A
L19Alpine ValleyLunar graben49.0N3.0E165
L20PosidoniusFloor-fractured crater31.8N29.9E95
L21FracastoriusCrater with subsided and fractured floor21.5S33.2E124
L22Aristarchus plateauMysterious uplifted region mantled with pyroclastics26.0N51.0W150
L23PicoIsolated Imbrium basin-ring fragment45.7N8.9W25
L24Hyginus RilleRille containing rimless collapse pits7.4N7.8E220
L25Messier & Messier AOblique ricochet-impact pair1.9S47.6E11
L26Mare FrigorisArcuate mare of uncertain origin56.0N1.4E1600
L27Archimedes Large crater lacking central peak29.7N4.0W83
L28HipparchusFirst drawing of a single crater5.5S4.8E150
L29Ariadaeus RilleLong, linear graben6.4N14.0E250
L30SchillerPossible oblique impact51.9S39.0W180
L31TaruntiusYoung floor-fractured crater5.6N46.5E56
L32Arago Alpha & BetaVolcanic domes6.2N21.4E26
L33Serpentine RidgeBasin inner-ring segment27.3N25.3E155
L34Lacus MortisStrange crater with rille and ridge45.0N27.2E152
L35Triesnecker RillesRille family4.3N4.6E215
L36Grimaldi basinA small two-ring basin5.5S68.3W440
L37BaillyBarely discernible basin66.5S69.1W303
L38Sabine and RitterPossible twin impacts1.7N19.7E30
L39SchickardCrater floor with Orientale basin ejecta stripe44.3S55.3W227
L40Janssen RilleRare example of a highland rille45.4S39.3E190
L41Bessel rayRay of uncertain origin near Bessel21.8N17.9EN/A
L42Marius HillsComplex of volcanic domes & hills12.5N54.0W125
L43WargentinA crater filled to the rim with lava or ejecta49.6S60.2W84
L44MerseniusDomed floor cut by secondary craters21.5S49.2W84
L45MaurolycusRegion of saturation cratering42.0S14.0E114
L46Regiomontanus central peakPossible volcanic peak28.0S0.6W124
L47Alphonsus dark spotsDark-halo eruptions on crater floor13.7S3.2W119
L48Cauchy regionFault, rilles and domes10.5N38.0E130
L49Gruithuisen Delta and GammaVolcanic domes formed with viscous lavas36.3N40.0W20
L50Cayley PlainsLight, smooth plains of uncertain origin4.0N15.1E14
L51Davy crater chainResult of comet-fragment impacts11.1S6.6W50
L52CrugerPossible volcanic caldera16.7S66.8W45
L53LamontPossible buried basin4.4N23.7E106
L54Hippalus RillesRilles concentric to Humorum basin24.5S29.0W240
L55BacoUnusually smooth crater floor and surrounding plains51.0S19.1E69
L56Australe basinA partially flooded ancient basin49.8S84.5E880
L57Reiner GammaConspicuous swirl and magnetic anomaly7.7N59.2W70
L58Rheita ValleyBasin secondary-crater chain42.5S51.5E445
L59Schiller-Zucchius basinBadly degraded overlooked basin56.0S45.0W335
L60Kies PiVolcanic dome26.9S24.2W45
L61Mosting ASimple crater close to the center of the moon’s near side3.2S5.2W13
L62RumkerLarge volcanic dome40.8N58.1W70
L63Imbrium sculptureBasin ejecta near and overlying Boscovich and Julius Caesar11.0N12.0E
L64DescartesApollo 16 landing site; putative region of highland volcanism11.7S15.7E48
L65Hortensius domesDome field north of Hortensius7.6N27.9W10
L66Hadley RilleLava channel near Apollo 15 landing site25.0N3.0E
L67Fra Mauro formationApollo 14 landing site on Imbrium ejecta3.6S17.5W
L68Flamsteed PProposed young volcanic crater and Surveyor 1 landing site3.0S44.0W112
L69Copernicus secondary cratersRays and craterlets near Pytheas19.6N19.1W4
L70Humboldtianum basinMulti-ring impact basin57.0N80.0E650
L71Sulpicius Gallus dark mantleAsh eruptions northwest of crater19.6N11.6E12
L72Atlas dark-halo cratersExplosive volcanic pits on the floor of Atlas46.7N44.4E87
L73Smythii basinDifficult-to-observe basin scarp and mare2.0S87.0E740
L74Copernicus HDark-halo impact crater6.9N18.3W5
L75Ptolemaeus BSaucer-like depression on the floor of Ptolemaeus8.0S0.8W16
L76W. BondLarge crater degraded by Imbrium ejecta65.3N3.7E158
L77Sirsalis RilleProcellarum basin radial rilles15.7S61.7W425
L78Lambert RA buried “ghost” crater23.8N20.6W54
L79Sinus AestuumEastern dark-mantle volcanic deposit12.0N3.5W90
L80Orientale basinYoungest large impact basin19.0S95.0W930
L81Hesiodus AConcentric crater30.1S17.0W15
L82LinneSmall crater once thought to have disappeared27.7N11.8E2.4
L83Plato craterletsCrater pits at limits of detection51.5N9.4W101
L84PitatusCrater with concentric rilles29.8S13.5W97
L85Langrenus raysAged ray system8.9S60.9E132
L86Prinz RillesRille system near the crater Prinz27.0N43.0W46
L87HumboldtCrater with central peaks and dark spots27.0S80.9E207
L88PearyDifficult-to-observe polar crater88.6N33.0E74
L89Valentine DomeVolcanic dome30.5N10.1E30
L90Armstrong, Aldrin and CollinsSmall craters near the Apollo 11 landing site1.3N23.7E3
L91De Gasparis RillesArea with many rilles25.9S50.7W30
L92Gylden ValleyPart of the Imbrium radial sculpture5.1S0.7E47
L93Dionysius raysUnusual and rare dark rays2.8N17.3E18
L94DrygalskiLarge south-pole region crater79.3S84.9W162
L95Procellarum basinThe Moon’s biggest basin?23.0N15.0W3200
L96Leibnitz MountainsRim of South Pole-Aitken basin85.0S30.0E
L97Inghirami ValleyOrientale basin ejecta44.0S73.0W140
L98Imbrium lava flowsMare lava-flow boundaries32.8N22.0W
L99InaD-shaped young volcanic caldera18.6N5.3E3
L100Mare Marginis swirlsPossible magnetic field deposits18.5N88.0E

How to Find All 100 Features

The first step, of course, is to have the list at your side. You can download the PDF version using the link at the bottom of this article.

On its own, unless you’re comfortable with the lunar coordinate system, the list is not hugely helpful for actually finding the objects. For that, you’re going to need a visual guide.

Visual Guide

There are some free moon-map resources on the internet, such as Google Moon and Rükl Maps. Both of these can be used to plot the features you plan to hunt for.

Then, of course, you could invest in a lunar map. As the name suggests, this is a map of the moon. I have owned one for many years and it is a great guide, but plotting 100 different features onto it to then find is not so simple.

What none of these options give you is a clear, unambiguous guide to the details and location of each individual feature. That’s why we developed the Guide to the Lunar 100.

Guide to The Lunar 100

Our guide to the Lunar 100 comes with everything you’ll need to successfully find, observe, and record all 100 challenges on the list. That includes a guide to the best nights to see each of the one hundred targets based on the moon’s phase.

Perhaps the most useful element though is the detailed, annotated NASA images of the lunar surface. Four whole-moon maps show the lunar surface at waxing crescent, first quarter, last quarter, and waning crescent, so you can see which features are best observed at which time.

Each of those four whole-moon images is then zoomed into with a further 14 detailed maps. See an example of a whole moon map and a zoomed-in area so you can see the detail and precision of what’s included in the guide. Click on each image to see a full-size version.

Lunar 100 features visible at waxing crescent phase
Whole moon map showing waxing crescent features. Note boxes for Zoom Maps A and B. Click for full-screen.
Zoomed-in view of lunar 100 features during waxing crescent.
Zoom Map A, showing the location of all the lunar 100 features in this area. Click for full-screen.

In total, there are 18 high-definition lunar maps with precise locations for all features clearly marked.

Some of the later features in the list are dastardly and even these detailed maps might not make it clear enough what you are searching for. That’s why we also included more detailed guidance for each feature on a printable PDF. Using the PDF with the maps means you’ll quickly discover exactly the right feature every time.

Lunar 100 detailed guidance notes
Extract of detailed guidance notes from within the Lunar 100 guide

Finally, you’ll need somewhere to record your lunar voyage of discovery, which is why our guide contains printable recording sheets. You can note when and how you discovered each feature as you go.

If you’re ready to take on this epic challenge, click here to purchase our low-priced Guide to the Lunar 100.

Summary

Chasing down the Lunar 100 is an epic challenge that any of us can take on, no matter where in the world we live, or even if we do our astronomy in an urban area.

You will need a telescope to complete the whole list. Binoculars will show many of the larger features, and a small telescope reveals almost everything else. However, for the most intricate areas, you’ll need a 6″ model to reveal the fine structures, small hills, and tiniest craters.

However you tackle the Lunar 100, let our guide help you, and have fun!

Download

Click the button below to download the whole Lunar 100 list as a PDF.


Written by Adam Kirk

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