Story by Genevive Bjorn
Photo by Ethan Tweedie
Here’s the recipe: clean skies, rain showers, a bright moon
and an angle 42 degrees. Nearly everyone has seen a rainbow, but few have
seen—or even heard of— a rainbow at night. Moonbows, or lunar rainbows, appear
as full arcs across the night sky, usually in pale pastels, silver or white.
But conditions in Hawai‘i can be so exceptional that the bright daytime colors
often also appear at night.
Hawai‘i is one of the few places in the world with a
reputation for exquisite moonbows. Indeed, the Hawaiians have been observing
anuenue kau po (rainbows appearing at night) for centuries. The Islands are
blessed with clean air, and tradewinds bring frequent rain showers.
Don Olson, professor of physics at Texas State University,
explains that a moonbow can appear when it rains during a full or nearly full
moon. They usually occur in one of two situations: if the moon is rising low in
the east and it’s raining to the west of the observer, or if the moon is high
in the west and setting while it’s raining to the east of the observer. A
moonbow will bloom in the rain shower at a spot 42 degrees (about half of a
right angle) in the direction opposite the moon.
For those in Hawai‘i, the choice locations for moonbow-spotting
are where windward meets leeward. During moonset on Maui, try Ho‘okipa lookout,
the Pa‘ia side of Ha‘iku or driving up to Pukalani on Haleakala Highway.
Moonbows are most likely to appear when the moon is setting near Kamuela on the
Big Island and Kahuku on the North Shore of O‘ahu. During moonrise, locations
along Kaua‘i’s Na Pali coast are ideal.
Chasing moonbows isn’t the only way to see them. You can
make one with a garden hose. When a bright moon is high in the sky, spray a
fine mist toward a dark spot, such as a wall or bush, away from the shadow of
your head. The ethereal arc should appear.