The Moon: Fourth Quadrant (South-east)
T
he Fourth Quadrant is made up mainly of highland,
though it does contain the Mare Nectaris, part of the
Mare Foecunditatis and the irregular limb-sea Mare
Australe. There are some large ruined enclosures such as
Janssen and Hipparchus, and three imposing formations
in a group – Theophilus, Cyrillus and Catharina. We also
find four members of the great Eastern Chain: Furnerius,
Petavius, Vendelinus and Langrenus. There are two crater-
valleys, those of Rheita and Reichenbach, plus the fasci-
nating little Messier, which was once (wrongly) suspected
of recent structural change. The feature once called the
Altai Mountain range is now known as the Altai Scarp,
which is certainly a better name for it; it is concentric
with the border of the Mare Nectaris, and runs north-west
from the prominent crater Piccolomini.AlfraganusA small, very bright crater; minor ray-centre.
AliacensisThis crater and its neighbour Wernerare very regu-
lar. There are several rather similar crater-pairs in the Fourth
Quadrant; others are Abenezra-Azophiand Almanon-Abulfeda.
CapellaCrater cut by a valley, with a particularly large cen-
tral peak with summit pit. Adjoins Isidorus, of similar size.
FracastoriusA great bay opening out of the Mare Nectaris.
Its seaward wall has been virtually destroyed. Between it
and Theophilus is a smaller bay, Beaumont.Goclenius. A fairly regular crater, making up a group with
less perfect Gutenbergand deformed Magelhaens.
HipparchusA very large enclosure not far from Ptolemaeus.
It is very broken, but under low light is still impressive. It
adjoins Albategnius, which is rather better preserved and
has a low central peak.
Humbolt, WilhelmA huge formation, too foreshortened to be
well seen – though the space probe pictures show that it has
considerable floor detail, including a system of rills. It adjoins
the smaller formation of Phillips, which is of similar type.
JanssenA vast enclosure, but in a very poor state of repair.
Its walls are broken in the north by Fabriciusand in the
south by the bright-walled Lockyer.
LangrenusOne of the great Eastern Chain. It has high,
terraced walls, rising to over 3000 metres (10,000 feet), and a
bright twin-peaked central elevation. Near full moon,
Langrenus appears as a bright patch. Disturbances inside
Langrenus have been photographed by A. Dollfus – the best
proof to date of the reality of lunar transient phenomena.
MädlerA prominent though irregular crater on the Mare
Nectaris. It is crossed by a ridge.
MessierThis and its twin, Messier A (formerly known as W.
J. Pickering) lie on the Mare Foecunditatis. They show
remarkable changes in appearance over a lunation, though
there has certainly been no real change in historic times.
The unique ‘comet’ ray extends to the west.
MetiusA well-formed walled plain near Janssen.
OkenA crater along the limb from the Mare Australe, easy
to identify because of its darkish floor.
PetaviusA magnificent crater – one of the finest on the
Moon. Its walls rise to over 3500 metres (11,500 feet) in
places; the slightly convex floor contains a complex central
mountain group, and a prominent rill runs from the centre
to the south-west wall. Oddly enough, Petavius is none too
easy to identify at full moon. Immediately outside it is
Palitzsch, once described as a ‘gorge’. In fact, it is a crater-
chain – several major rings which have coalesced.
PiccolominiThe prominent, high-walled crater at the arc of
the Altai Scarp.
RheitaA deep crater with sharp walls. Associated with it is
the so-called ‘Valley’ over 180 kilometres (110 miles) long
and in places up to 25 kilometres (15 miles) broad; it is not
a true valley, but is made up of craterlets. Not far away is
the Reichenbachvalley, which is of similar type but is not so
conspicuous or so well-formed.
SteinheilThis and its neighbour Wattmake up a pair of
‘Siamese twins’, not unlike Scheiner and Blancanus in the
Third Quadrant.
StöflerA grand enclosure, with an iron-grey floor which
makes it easy to find. Part of the rampart has been
destroyed by the intrusion of Faraday.
Theon Seniorand Theon Junior. Very bright craterlets near
the regular, conspicuous Delambre. In many ways they
resemble Alfraganus.
TheophilusOne of the most superb features of the Moon,
and in every way the equal of Copernicus except that it is
not a ray-centre. It is very deep, with peaks rising to 4400
metres (14,400 feet) above the floor. There is a magnificent
central mountain group. It adjoins Cyrillus, which is less
regular and in turn adjoins very rough-floored Catharina.
Vendelinus. A member of the Eastern Chain, but less
regular than Langrenus or Petavius, and presumably older.
It has no central peak, and in places the walls are broken.
VlacqA deep, well-formed crater with a central peak; it is a
member of a rather complex group, of which other mem-
bers are Hommeland Hagecius.
WebbA crater very near the lunar equator, with a darkish
floor and a central hill; centre of system of short, faint rays.ATLAS OF THE UNIVERSE
SELECTED CRATERS: FOURTH QUADRANT
Crater Diameter, Lat. °S Long. °E
km
Abenezra 43 21 12
Abulfeda 64 14 14
Airy 35 18 6
Alfraganus 19 6 19
Aliacensis 84 31 5
Apianus 63 27 8
Azophi 43 22 13
Barocius 80 45 17
Beaumont 48 18 29
Blanchinus 53 25 3
Boguslawsky 97 75 45
Bohnenberger 35 16 40
Brisbane 47 50 65
Buch 48 39 18
Büsching 58 38 20
Capella 48 8 36
Catharina 89 18 24
Cyrillus 97 13 24
Delambre 52 2 18
Demonax 121 85 35
Donati 35 21 5
Fabricius 89 43 42
Faraday 64 42 18
Faye 35 21 4
Fermat 40 23 20
Fernelius 64 38 5
Fracastorius 97 21 33
Furnerius 129 36 60
Goclenius 52 10 45
Gutenberg 72 8 41
Hagecius 81 60 46
Halley 35 8 6
Hecataeus 180 23 84
Helmholtz 97 72 78
Hind 26 8 7
Hipparchus 145 6 5
Albategnius 129 12 4
Hommel 121 54 33
Horrocks 29 4 6
Humboldt, 193 27 81
Wilhelm
Isidorus 48 8 33
Janssen 170 46 40
Kant 30 11 20
La Caille 53 24 1
Langrenus 137 9 61Crater Diameter, Lat. °S Long. °E
km
La Pérouse 72 10 78
Legendre 74 29 70
Licetus 74 47 6
Lilius 52 54 6
Lindenau 56 32 25
Lockyer 48 46 37
Maclaurin 45 2 68
Mädler 32 11 30
Magelhaens 40 12 44
Manzinus 90 68 25
Marinus 48 40 75
Messier 13 2 48
Metius 814044
Mutus 81 63 30
Neander 48 31 40
Nearch 61 58 39
Oken 80 44 78
Palitzsch 97 32 28 64
Parrot 64 15 3
Petavius 170 25 61
Phillips 120 26 78
Piccolomini 80 30 32
Pitiscus 80 51 31
Playfair 43 23 9
Pons 32 25 22
Pontécoulant 97 59 65
Rabbi Levi 80 35 24
Réaumur 45 2 1
Reichenbach 48 30 48
Rheita 68 37 47
Riccius 80 37 26
Rosse 16 18 35
Sacrobosco 84 24 17
Steinheil 70 50 48
Stevinus 70 33 54
Stöfler 145 41 6
Tacitus 40 16 19
Theon Junior 16 2 16
Theon Senior 17 1 15
Theophilus 101 12 26
Torricelli 19 5 29
Vendelinus 165 16 62
Vlacq 90 53 39
Watt 72 50 51
Webb 26 1 60
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