Blue Moon

To the unaided eye the moon does not look colorful; it appears to be just different shades of gray. However, the rocks that make up the lunar surface are not the same everywhere, and different minerals have slightly different colors. With a digital photo we can make the differences obvious by strongly amplifying color saturation without changing hues or brightness levels. The lunar highlands become yellow and orange while the basalts of the maria turn blue (fitting, given that they were once thought to be oceans). Only large craters and the material ejected from them are neutral gray or white.

 

For this picture 50 frames were captured. The camera was on a tripod; it did not track the sky. Aligning the frames and computing the mean yielded a single image with a higher signal to noise ratio. One copy of the mean image was strongly sharpened to reduce blurring caused by atmospheric distortion. This produced the version of the moon seen on the left. In a second copy of the mean image color saturation was amplified, but no sharpening was applied. Combining the luminance of the sharpened image with the colors of the saturated image produced the version of the moon seen on the right.

Done