Earthshine blog

The Moon is occasionally present in corners of images of the Earth taken by Earth Observation satellites. Use such images and the known colours of the Moon to link the filter system used by the satellites to the Johnson UBV system. Use the resulting tool to calculate B-V colours of the Earth through time. Map out seasonal variability. Test sensitivity of the result to imposed variations in e.g. ice cover (by image manipulation) or similar for desertification.

I have looked through all suitable images close to full moon (i.e. at high Sun-Earth-Moon angle) and only came up with a few relevant nights, all within 10 degrees of full moon. We were keen to make a colour map across the face for figuring out what colour range is there, and what colours are reflected under BS sunlight, rather than DS Earthlight.

JD2455814: is the best full moon data available — it’s shown on the left. We ran it through our colour pipeline and get a B-V ~ 0.9. The B and V images turn out to be slightly different sizes, which made the colour map hard to produce. Later it has turned out that this may be due to distortions introduced in the shift to align the images at all. Work is proceeding on this.

JD2455905: data taken when we were following an eclipse — Dec 09, 2011, total lunar eclipse. No non-eclipsed images, so nothing useful on the Brightside colour night (we should check the Moon is red though).

JD2456082 is also eclipsed — partially. No useful colour data as we have only eclipsed images. June 3, 2012

JD2455847 looked like a promising night — full moon at an airmass of 1.54. However, when I make a colour map (right panel above), it has a B-V of ~0.4 across the face. Can only assume that the exposure times are wrong in the headers (as has happened occasionally). One corner of the moon is slightlty eclipsed for
some odd reason in one filter only (V) — opposite Tycho. Perhaps we hit
the dome in this filter? These data should clearly not be trusted further.