Earthshine blog

Earthshine blog

"Earthshine blog"

A blog about a system to determine terrestrial albedo by earthshine observations. Feasible thanks to sheer determination.

Brightness of opposite sides of the Moon

Data reduction issuesPosted by Chris Flynn Sep 19, 2012 11:10AM
We have isolated the very best images in V band, in which the Moon is well centered and well exposed.

We measure the apparent magnitude of the moon in these images by simply measuring the total flux, and applying the standard photometry relations (i.e.

We correct for extinction of 0.10 mag/airmass (from

We then compare the apparent magnitude to the expected apparent V magnitude from the JPL ephemeris for the Moon ( This uses the relation quoted in Allen "Astrophysical Quantities", which actually comes from Eqn 8 of this paper:

The plot shows the difference in the apparent magnitude as a function of phase (new moon = 0). Blue and green show opposite sides of the moon.

There is a bit of scatter in these data, but there are two clear sequences around phases 50 to 100 showing that opposites sides of the moon differ in luminosity by about 0.1 mag. This is quite a lot less than we expected to see, viz. this post:

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