A penumbral eclipse is a lunar eclipse in which the Moon passes only through Earth's faint outer shadow, the penumbra, and misses the dark umbra. The Moon dims so slightly that most people notice nothing, except near mid-eclipse, when one edge looks faintly shaded. Roughly a third of all lunar eclipses are penumbral.
Understanding Penumbral Eclipse
Why a penumbral eclipse is so faint
From a point on the Moon inside Earth's penumbra, part of the Sun's disc is still in view. Even with half of it hidden, the Moon is lit at half strength, and the eye is poor at noticing a change like that on a bright object. The shading becomes noticeable only when roughly two thirds of the Moon is in the penumbra, and then mostly on the edge nearest the umbra, where more of the Sun is hidden. That is why a shallow penumbral eclipse can pass with no visible change at all.
The penumbral eclipses of 2027
All three, from first to last penumbral contact, in UTC. Each page shows where the Moon is up and the local times:
| Date | Seen from | Penumbral contacts (UTC) |
|---|---|---|
| 20 February 2027 | Europe, Africa, the Middle East, South Asia; the eastern Americas at moonrise | 21:11 to 01:13, about 4 h |
| 18 July 2027 | South and East Asia, Australia, New Zealand; so slight it is practically invisible | 15:50 to 16:15, about 25 min |
| 17 August 2027 | The Americas, the Pacific; New Zealand and eastern Australia at moonrise | 05:23 to 09:03, about 3 h 40 min |
How to spot one
Watch the edge of the Moon nearest the umbra around the time of greatest eclipse, and compare it with the opposite edge. A camera on fixed settings, taking a shot an hour before mid-eclipse and another at mid-eclipse, shows the difference far better than the eye. Of the three in 2027, 20 February is the one to try: it is the longest and the Moon passes deepest into the penumbra.