Brightness of Selected Features

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Lunar Brightness

(see glossary entry: Albedo feature)


Description

The Moon is a place of strong brightness variations, sometimes seen in one view while looking at a brilliant peak sticking up from a black shadow. But the only way to make consistent and reliable determinations of lunar brightness is to observe at full Moon, when the Sun and the Earth see the Moon from nearly the same angle.

Brightness Comparison

There are two ways to determine lunar brightness - visual estimates and photometric measurements. The great German observer Johann Schröter developed the visual scale that was popularized by Thomas Elger in the late 1880's. Photoelectric photometry started in the 1920's and is now done not just for a single spot on the lunar surface, but with ccd detectors, for broad areas. The weakness of the visual estimates is their subjectivity. Nonetheless, the old visual estimates and old spot measurements still have value. Here is a comparison of the visual brightness scale, N (0 is the absolute black of shadows and 10 is the brightest spot on the Moon - the central peaks of Aristarchus) and measured albedos (A) - the measured reflectivity of the surface (0 means incident light is totally absorbed - like a black hole; 1.0 means 100% of incident light is reflected). This table comes from the article "Photometry of the Moon" by VG Fessenkov in the 1962 book Physics and Astronomy of the Moon (edited by Z Kopal). - tychocrater Sep 3, 2007

Feature
Brightness Scale (N)
Albedo (A)

Grimaldi & Riccioli floors

1.0
0.061

Boscovich floor

1.5
0.067

Julius Caesar & Endymion floors

2.0
0.074

Pitatus & Marius floors

2.5
0.081

Taruntius, Plinius, Flamsteed, Theophilus, Mercator floors

3.0
0.088

Hansen, Archimedes & Mersenius floors

3.5
0.095

Ptolemaeus, Manilius & Guericke floors

4.0
0.102

Aristillus environs

4.5
0.109

Arago, Lansberg & Bullialdus walls, Kepler environs

5.0
0.115

Picard & Timocharis walls, rays of Copernicus

5.5
0.122

Macrobius, Kant, Bessel, Mösting & Flamsteed walls

6.0
0.129

Lagrange, Mons La Hire & Theaetetus walls

6.5
0.135

Theon Junior, Ariadaeus, Behaim & Bode B walls

7.0
0.142

Euclides, Ukert & Hortensius walls

7.5
0.149

Godin, Copernicus & Bode walls

8.0
0.156

Proclus, Bode A & Hipparchus C walls

8.5
0.163

Mersenius & Mosting A walls

9.0
0.169

Aristarchus interior

9.5
0.176

Aristarchus central peaks

10.0
0.183


The approximate mathematical relation between visual brightness estimate, N, and measured albedo, A is:

  • A = 0.047 - 0.136 x N


Additional Information


LPOD Articles


Bibliography

Brightness of Lunar Features, Chuck Wood's Moon Web site