On Monday night, serious moon viewers may notice something different about the moon — if you look hard enough.

The full moon will be a blue supermoon, a celestial occurrence that combines two events: a supermoon, which is when the moon is closest to the Earth; and a blue moon, the third of fourth full moons in a single season.

The cosmic event usually happens about once every 10 years, but there was a super blue moon last August as well. NASA determined that the moon had met the criteria for this seemingly rare event two years in a row.

How to see Monday’s blue supermoonMonday’s supermoon will reach its full peak at 2:26 p.m. EDT, according to NASA, but you might not even notice the difference that night if you aren’t careful.

“I personally can’t tell the difference between a supermoon and a regular moon,” Fred Espenak, a scientist emeritus for NASA’s Goddard Space Flight Center, told Morning Edition. “And I’ve been looking at the moon all my life.”

If you’re after a large moon view, you can watch the moon rise or set in your area. The moon will appear bigger if you watch it rise in the east, or watch the moon set in the west. The larger moon, combined with foreground objects in your area will create a “moon illusion” and make the moon appear bigger.

You can check the local rising and setting times for your area using the U.S. Navy’s Moonrise calendar.

If you want a more detailed view of the moon, you can use a telescope or a pair of binoculars. The moon will appear full for three days, according to NASA, but only Monday’s will be a true supermoon.