July 4, 2020: The Moon is about to pass through the shadow of Earth, producing a penumbral lunar eclipse. Unfortunately, it might be invisible.
Eclipse expert Fred Espenak explains: “During past lunar eclipses, I have made a concerted effort to determine when I can first see the subtle shading of Earth’s penumbral shadow on the Moon (using naked eye and binoculars). I have consistently found the penumbral shading is only detectable when at least 2/3 of the Moon lies within the penumbral shadow.”
“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,” he says. “Digital photography can reveal the subtle shading if the contrast of the image is greatly increased.
Penumbral eclipses differ from total eclipses as follows: In a total lunar eclipse, the Moon passes directly through the darkest crimson-colored core of Earth’s shadow. It produces a “Blood Moon.” In a penumbral lunar eclipse, the Moon passes through the pale outskirts of Earth’s shadow. Penumbral eclipses are notoriously subtle–and in this case potentially invisible.
“I fear the general media is hyping this event when there’s really nothing more to see than a Full Moon–although that’s beautiful in its own right,” he says.