Sky & Telescope - December 2019 - 52

DECEMBER 2019 OBSERVING
Exploring the Moon by Charles Wood

Limb Huggers
These interesting craters require a strong northwest libration
and steady atmospheric conditions.

I

s Lavoisier the only lunar crater
named for a scientist who faced the
guillotine? The brilliant French chemist
famed for his recognition that oxygen
is a chemical element, Antoine-Laurent
Lavoisier was one of many nobles who
lost their heads during the French Revolution. But the crater Lavoisier remains
along the western limb of the Moon,
ironically near von Braun, another
noble who supported a deposed regime.
These two craters are so near the
limb (about 80°W longitude) that they
appear as foreshortened ellipses and are
rarely observed. Yet the larger craters
Gauss and Humboldt are both near

80°E longitude and frequently targeted
by observers. The latter two craters
are twice as big as Lavoisier and von
Braun, and are readily observed in early
evenings, while the western limb craters
are best seen from full Moon until
almost new Moon, progressively later
in the night and early in morning. But
there are other possible explanations for
the slight. Most observers may not realize how interesting these noble craters
are and thus haven't tried to find them.
The Lavoisier region is just inland
from the western reaches of Oceanus
Procellarum. Two 20- to 30-km-wide
craters on this vast mare, Harding and

The Lavoisier crater group
including von Braun along
the western edge of Oceanus Procellarum is best
seen under the most favorable lunar librations.

Lavoisier A, are conspicuous markers to
the area of interest just to their west.
The group contains five main craters
of interest. The largest is Lavoisier, a
roughly 70-km-wide, 600-meter-deep
degraded crater bearing many classic features of a floor-fractured crater.
Lavoisier's floor contains a concentric
inner ridge, concentric rilles, and an
annular swath of mare lava, as well
as a small but beautiful concentric
crater. Von Braun is next biggest at 60
km diameter and 1.6 km deep. Less
degraded than Lavoisier, von Braun's
rim is best seen just before full Moon.
The Lunar Reconnaissance Orbiter
QuickMap (https://is.gd/SM5NY1)
shows that von Braun has a domed
central floor elevated by about 300 m.
The eastern half of the floor is smooth
but not dark, while the western floor is
sliced by eight non-concentric rilles.
Next is 51 km Lavoisier E, another
classic floor-fractured crater with a high
eastern rim that abuts von Braun. It
contains a broad wreath of concentric
rilles circling a lava-flooded inner floor
surrounding a central peak. The mare
patch is visible in mid-sized telescopes.

Harding

Lavoisier

Lavoisier A

52

D EC E M B E R 2 019 * SK Y & TELESCOPE

N ASA / GSFC / A RIZON A STATE UNIV ERSIT Y
CREDIT

von Braun


https://www.is.gd/SM5NY1

Sky & Telescope - December 2019

Table of Contents for the Digital Edition of Sky & Telescope - December 2019

Contents
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Sky & Telescope - December 2019 - Cover2
Sky & Telescope - December 2019 - 1
Sky & Telescope - December 2019 - Contents
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