Crescent Moon with Earthshine

One evening I had just gone up to my roof to look at the night sky and noticed the crescent Moon with that Earthshine glow you see when it is not too many days after New Moon. The shaded side of the Moon is actually lit by sunlight reflected from Earth, hence named Earthshine. Quickly decided that it was a photo opp! Set up the camera (Canon EOS 1Ds) with the scope at f/10 (2030mm focal length) and started snapping away. Quickly found out that there's no way to satisfactorily capture what your eyes see on one frame. The required dynamic range is just too vast. So I then started exposing for the crescent separately from the Earthshine side; with the intention of later compositing the two. Here are the two frames I finally settled on, first the Earthshine side, 3 seconds exposure at ISO 1250:

Notice how burnt out the crescent is. To expose the crescent "correctly" I had to use an exposure of 1/15th second, but then that sunlit side does not look bright enough! So I settled for a frame exposed for 1/5th second:

Combining the two yields this:

The compositing was actually quite difficult to do seamlessly. Because the Moon by then was getting closer to the horizon, the atmosphere did not give clean edges, but introduced a reddish fringe, seen in the top photo. Secondly the thickness of the crescent itself depended on the exposure! Less exposure, thinner. Anyway with the use of judicious masking I was able put the two together reasonably well. Thereafter I adjusted the colour balance to get rid of the brownish (sunset) tones. I think it now replicates quite well what you would see through binoculars. Well, sort of...

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