Comet Lemmon is moving quickly west of the Big Dipper, near bright Arcturus, while Comet SWAN lies beneath the three stars that form the Summer Triangle. About 90 minutes after sunset is when to look for both.

Astronomer Gianluca Masi captured spectacular footage of a glowing meteor trail wrapping around the colossal tail of Comet Lemmon on Oct. 24, as the wandering solar system body approached the constellation Serpens Caput in Earth's sky.

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The green-hued Comet Lemmon will align with the Serpens constellation this weekend, offering a stunning view for astronomy lovers.

Lemmon, which is a rare green comet, can be seen with the naked eye on Oct. 21, according to the Royal Astronomical Society, with peak visibility near Halloween. SWAN may be visible using binoculars or a telescope, according to Starwalk, a real-time astronomical app for stargazing.

The comets are visible in the northwest (Lemmon) and southwest (SWAN) about 90 minutes after sunset. Lemmon is moving quickly across the sky west of the Big Dipper, close to bright star Arcturus, while SWAN is beneath the three bright stars that comprise the Summer Triangle. At magntitude +4.4, Lemmon is by far the brighter and easiest to see.

A newly discovered comet is about to make its closest pass to Earth on Tuesday night. It should be visible over the Bay Area before it disappears — and won’t be seen again for more than a thousand years.

Comets Lemmon and SWAN are nearing Earth in a rare double cosmic treat. Where and what time can you see them? What to know.

Brooks, which visits the Earth roughly every 71 years, was spotted releasing intriguing radio signals last year.