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 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


This page has been edited 8 times. The last modification was made by - JimMosher JimMosher on Jan 9, 2010 1:44 pm - mgx2