Here is a nice pic of the Moon, just entering totality during the recent Lunar eclipse which began on the night of 20 December, and reached its peak darkness in the early AM of the 21st. The entire Moon is inside the Earth’s shadow, but with a slight bluish tone apparent on the receeding limb, still getting a bit of diffuse sunlight exposure. This blueness of the Moon’s limb is most apparent on the diminishing sunlit parts during a Lunar eclipse, especially just before it goes fully dark, when the thin Lunar plasma atmosphere is subjected to only a small amount of light exposure and excitation from the Sun. The photo is of course a time-exposure of nearly a half-minute, which helps to intensify the colors. At this time of the photograph, the disk of the Moon could hardly be seen with the naked eye.
Here’s what NASA says about the color of the Moon during Lunar eclipses, which apparently should be shielded from any bluish frequencies:
White light from the Sun is a mixture of all the colors of the rainbow. When a ray of "white" sunlight passes at grazing incidence through Earth’s atmosphere, molecules and aerosols in the air scatter blue light in all directions (this is why the sky is blue). The remaining reddish light is bent (refracted) into Earth’s umbral shadow zone, giving the eclipsed Moon a coppery glow.
You’ve heard the phrase "Blue Moon", or "once in a Blue Moon" to signify a very rare event… and indeed the "blueness" of the thin and rarified ionized-plasma and electrostatically-charged Lunar atmosphere is typically something not routinely observed. Frequently, atmospheric dusts or fire-smoke will also yield up a blue coloration to the moon, but that is not what is happening in the case of the blue-edge effect during a Lunar eclipse, as shown in the above photo. (See my discussion on other blue-glowing Lunar anomalies here.) This phenomenon is not given much attention by mainstream astronomy, as it appears to be an anomaly. And it isn’t going to be easily observed or photographed unless one actually looks for it, makes an effort to try and photograph it. One’s telescope lenses and imaging cameras must also be designed for full and natural color rendition.
The shot was made using a Meade 16" LX200R telescope with 24 second exposure, using a Kodak 4 mp digital camera, as taken through a Meade 4000 Super-Plössel 56mm eyepiece. The image was captured just before midnight at the OBRL Greensprings Observatory, at 4200′ elevation, east of Ashland in Southern Oregon, USA. It would have been of sharper focus and better color rendition except for a thin layer of cloud-haze at the time.
James DeMeo, PhD