For centuries it was said that the moon is made of green cheese, "green" referring not to the color green but to fresh, unripe cheese, which is pale yellow, pocked, mottled and round. Today this expression is still occasionally heard, generally used sarcastically - but we are reasonably sure now that the moon isn't made of cheese at all!
To the casual observer the moon appears to be shades of grey, perhaps with a yellowish tint. Through a good telescope one may discern subtle shades of blue, green and red, but the bright light of the sun on the highly reflective surface of the moon pretty well washes it out.
Astrophotography takes advantage of a telescope's ability to multiply the light emanating from faint, distant objects and a camera's ability to concentrate light through time exposure. But the telescope and camera can also be used together to tone down bright objects and make their true colors more apparent.
For this image of our close celestial companion, I acquired 18 separate exposures of 1/500 second each, at 1000 mm focal length, f/4.9 and ISO 200. No filters were used - the camera is a stock Canon Digital Rebel XT. The 18 separate images were aligned and overlaid with Iris software in order to reduce the blurring caused by atmospheric distortion. The resulting image was "stretched" using the hyperbolic arc-sin function in Iris in order to enhance subtle variations in texture and color. Finaly the contrast and color saturation were increased with Photoshop, resulting in this image.
This is not a false color image - the colors are real, but their saturations have been enhanced. The moon's surface is rich in minerals containing titanium and iron. The blue areas in this image are especially rich in titanium, while the orange areas are iron-rich. I think this image lays the "green cheese" theory to rest convincingly!
....By Don Reed
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