Impact crater

Bailly

A vast, battered formation near the southwestern limb. Foreshortening makes the interior much harder to inspect than the catalogue size might suggest.

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Bailly and surrounding lunar terrain in the LROC Wide Angle Camera mosaic
Bailly · North up, east right. Open image ↗
NASA / GSFC / Arizona State University · LROC WAC mosaic via USGS. Regional map crop; lighting is fixed and does not follow the selected date.
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Lunar north up, with geocentric libration. Full atlas mode shows the entire facing surface; switch to Selected phase for today’s illumination. Choose a different date in the atlas.

How to observe Bailly

Watch for favourable libration and low sunlight. Start by identifying the near rim; do not expect a face-on view.

Finding the region

Look at 66.82° S, 68.90° W on the lunar disc. The chart marker identifies the catalogue centre. Start with a wide field and use the nearby formations below as landmarks.

Equipment & conditions

Start at low magnification to identify the rim. Move to a moderate power when the air is steady; low sunlight usually makes walls and floor relief easier to distinguish. A bright ray system can be more conspicuous near full Moon.

Lighting

For surface relief, try a time when the Sun is low over this region. To compare surface brightness and any bright rays, return under higher illumination. The atlas calculates the solar elevation at the formation’s centre for any selected date.

View Bailly in the atlas

IAU / USGS Gazetteer

Official feature record

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Approved name
Bailly
Feature classification
Crater, craters
Catalogue diameter
300.56 km
Centre latitude
66.82° S
Centre longitude
68.90° W
Name origin (Gazetteer)
Jean Sylvain; French astronomer (1736-1793).

Coordinates are selenographic, with east-positive longitude. Dimensions are the Gazetteer’s catalogue values; for extended formations they do not represent a circular crater diameter. Data snapshot: 2026-09-16. Observing guidance above is separate from the official record.

Nearby formations

The four closest catalogue entries, measured from their centres.

LROC photograph of SchillerImpact crater

Schiller

A markedly elongated crater in the southwestern highlands. Its shape stands out among the more rounded neighbouring formations.

LROC photograph of SchickardImpact crater

Schickard

A broad walled plain in the southwestern lunar highlands. Different parts of its floor have noticeably different surface brightness.

LROC photograph of ClaviusImpact crater

Clavius

A large southern crater containing a distinctive curved sequence of smaller craters. The largest interior craters are visible well before the smaller craterlets.

LROC photograph of TychoImpact crater

Tycho

A crater in the southern highlands surrounded by bright impact rays. Its rim, central peak and terraced walls stand out against the older, densely cratered terrain.