With the fall equinox approaching, skywatchers have an opportunity to spot a celestial phenomenon called a "false dawn."

Also known as zodiacal light — meaning "light from the circle of animals" — this is a soft, hazy, glowing pyramid shape, appearing from the horizon.

It’s caused by sunlight being scattered by dust in the solar system. 

When to look for zodiacal light

Zodiacal light is visible just before sunrise — "true dawn" — which is how it got its name. The sweet spot is about 90 minutes before the sun makes an appearance.

This display is visible all of September and October, but it’s easiest to notice around the equinox on Sept. 22.

(MORE: Meteorological fall vs. fall equinox: Which is the best and why?)

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That’s because the ecliptic, the path the sun takes around the Earth, is angled to the horizon in a way that brings the glow even higher in the sky.

The darker the sky, the better, so a new moon would be the most ideal time to see it.

Unfortunately this year the equinox falls just three days before a full moon, and it will be 83% illuminated. 

If you can’t find it on the equinox, you can try again at the next new moon, on Oct. 10 — and you might even have better luck catching it then thanks to the darker sky.

How to find zodiacal light

In the Northern Hemisphere, you’ll want to look east into the sky. 

If you can go somewhere where there’s less light pollution and a wide open view that’s not obstructed by trees, that’s best.

(MORE: How to tell the difference between 'false' and true fall)

Some stargazing apps, like Sky Tonight, can help you find the ecliptic — the path the sun appears to take across the sky — which aligns with the zodiacal light.

'False dusk'

Around the spring equinox, the Northern Hemisphere sees the same effect but about 90 minutes after sunset, known as “false dusk.”

And everything is reversed in the Southern Hemisphere: False dawn happens in the spring and false dusk in the fall.

Content writer Ada Wood enjoys exploring the stories that science and climate teach us about our natural world and how it influences the way we live in it.