The July full moon will pass into the lightest part of the shadow of the Earth, which is called the penumbra. The penumbral lunar eclipse will thus see the moon's surface darken very slightly. But even if you can't see the eclipse that well, the moon is always a fun observing target.
The eclipse will start on tonight at 11:08 p.m. EDT (0308 GMT Sunday, July 5) and end on Sunday at 1:53 a.m. EDT (0553 GMT), according to In-the-Sky.org. At most, depending on your location, 35 percent of the visible moon will pass into the light shadow of the Earth. The reduced surface eclipse will make it even harder for amateurs to see the light eclipse unless you have good photographic equipment.
n general, most people don't notice the penumbral shadow projected on the moon until at least 70% of its diameter is covered," Space.com skywatching columnist Joe Rao said in our guide. "Some people who have very acute vision and better-than-average perception might notice an ever-so-slight shading when only 50% of the moon is inside the penumbra. But in the case of Saturday night, the obscuration amounts to just a tad over 35%; not enough to make any kind of visual impact."
Eclipse expert Fred Espenak gave Spaceweather.com a similar forecast. In fact, Espenak said, the lunar eclipse may be invisible.
"Because the Moon will only pass 1/3 of the way into Earth’s penumbral shadow during the July 4/5 lunar eclipse, it will NOT BE VISIBLE to the naked eye," Espenak told Spaceweather.com. "Digital photography can reveal the subtle shading if the contrast of the image is greatly increased."
Even if you can't spot the eclipse, though, there are other things in the sky that evening to enjoy.