July 26, 2014

Airbrushed Out?

image by Leo Aerts, Belgium

One reason the Moon always looks different when observing is that we almost always see it under different conditions of phase and libration. Here is a remarkable example of a feature being completely invisible in one image, but clearly there in another one with opposite illumination. On Leo's image from June 6th (left), the northern wall of the Bond Rille (on the floor of W.Bond) catches the sunlight while the southern wall casts a narrow matching shadow. The Bond Rille runs roughly east to west so that it is always somewhat difficult to see. I suppose that on July 18 when the Sun was shining from the opposite direction the illuminated wall was facing away from us and impossible to see. I didn't check if the Sun was further north or south in either of the images - a higher angle would make the thin trough slightly more visible. But it is interesting that neither image captured the similar width (but shallower) continuation of the rille that bends to the northwest towards the bright-rimmed crater Epigenes A at top right of the June image. No single image, from skilled amateurs or orbiting spacecraft can reveal all their is to see on the Moon.

Chuck Wood

Related Links
21st Century Atlas chart 10.

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