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Earthshine blog

"Earthshine blog"

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

More colour mapping

Showcase images and animationsPosted by Chris Flynn Dec 13, 2012 04:42AM
Following on from the previous post, we have made a colour map based on two images (V and B) taken on JD2456034


Both are averaged results from stacks of 100 exposures, so the S/N ratio is 10 times better compared to the images in the last post.

V band exposure time was 72.5 ms, and the B band exposure was 222 ms, for a total of 7.3 seconds in V and 22 seconds in B. The observations were at an airmass of ~ 2.3.

The colour map looks like this:

with the colour scale (B-V) running from 0.2 to 1.3.

The BS (brightside) has a colour of around 1.0, which is still a little redder than the expected value of 0.9 (for BS on a full moon) by van den Bergh (1962).

There is more scattering of the light in B than in V, which accounts for the deep valley to the right of the BS, and the excess halo light beyond it. Colours here are not reliable. Colours just beyond the concave edge of the crescent on the DS are probably also affected by differences in the scattered light profile, so should be regarded carefully (this part of the moon can be examined when the crescent is on the other side). The left half should be pretty good!

The DS (darkside) has colours ranging from about 0.6 to 0.9 -- with the lowlands redder than the highlands.

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