A fall harvest supermoon put on a rare celestial show Tuesday when it also created a partial lunar eclipse for skygazers around the world. The bright harvest supermoon — a full moon that happens around the autumnal equinox — entered Earth’s shadow around 10:13 p.

If you happened to notice the supermoon looking especially large as it was rising, you may have fallen victim to a “well-known, poorly studied optical illusion,” said NASA’s Noah Petro. Here’s the scientific explanation of what you were seeing,

Mainers can expect a vivid scene in the Tuesday night sky when a supermoon coincides with a partial lunar eclipse. NASA predicts that the full moon will be partially covered by Earth’s shadow for several hours Tuesday night.