The Moon passes in front of the Sun, at new Moon. It is total if the Moon hides it completely, annular if the Moon is too far to cover it (a ring stays visible), partial elsewhere. Never look at the Sun without certified eclipse glasses, except during the brief total phase.
ToolsThe Moon tonight
Related terms
- Lunar eclipse
The Moon passes through the Earth’s shadow, at full Moon. It can be penumbral (barely visible), partial or total; during totality the Moon turns coppery red, lit by light filtered through all the Earth’s sunsets. It is perfectly safe to watch with the naked eye.
- Solar filter
The only safe way to look at the Sun: a certified film or glass fixed securely over the front of the instrument, blocking more than 99.99% of the light. Never use a filter that screws onto the eyepiece: it can crack from the heat. A single glance through an unfiltered instrument causes blindness in a fraction of a second.
- Moon phases
The Moon’s changing look depending on how much of its sunlit side we see: new Moon, crescent, first quarter, gibbous, full Moon, then back again. The full cycle, the lunation, lasts 29.5 days. For relief, prefer the quarters to the full Moon, which looks flat.
← The whole glossary