Topline
Two comets are becoming brighter in the night sky this weekend — Friday, Oct. 17 through Sunday, Oct. 19 — and could be on the cusp of naked-eye visibility. Predicted to reach their peak brightness during the new moon and the Orionid meteor shower early next week, Comet Lemmon (also called C/2025 A6) and Comet SWAN (C/2025 R2) can be found after sunset in opposite parts of the sky. The brighter Comet Lemmon will glow in the northwest, while Comet SWAN will sit low in the southwest. For the best chance to see them, look during a 30-minute window beginning about 90 minutes after sunset — and bring binoculars.
Comet Lemmon (C/2025 A6) as imaged using a Seestar S30 smart telescope from New Brunswick, Canada, by Stéphane Picard at Cliff Valley Astronomy, on Oct. 4, 2025.
Stéphane Picard, Cliff Valley Astronomy (used with permission)
Key Facts
These are the first binocular comets since comet Tsuchinshan-ATLAS in Oct. 2024.
Comet Lemmon is the brighter of the two. According to the Comet Observation Database, Lemmon is shining at magnitude +4.9 and SWAN a little dimmer at +5.9 — almost bright enough to be seen from a very dark sky site with the naked eye, but binoculars will make all the difference. A pair of 8×42 or 10×50 binoculars is ideal.
Comet Lemmon was discovered on Jan. 3, 2025, by the Mount Lemmon Survey near Tucson, Arizona. It takes about 1,350 Earth-years to orbit the sun.
Comet SWAN was found much more recently, on Sept. 11, 2025, as it emerged from the sun’s glare. It takes about 22,500 years to complete a single orbit and is now moving away from the sun.
Both comets are visible to Northern Hemisphere observers this weekend — Lemmon in the northwest, SWAN in the southwest — roughly 90 minutes after sunset.
Use finder charts at In-The-Sky.com or apps like Sky Guide, Stellarium and SkySafari to find them easily.
The Nature Of Comets
Comets are unpredictable, either brightening suddenly — particularly when they get close to the sun — or dimming without warning, so it’s best to view them as soon as there’s a clear sky. “Comets love to defy expectations. While some fizzle, others become unexpected showstoppers,” said Franck Marchis, Senior Astronomer at the SETI Institute and Chief Science Officer at Unistellar, in an email. “C/2025 A6 (Lemmon) was an afterthought early in the year, but brightened dramatically this summer, likely as fresh ice was exposed. C/2025 R2 (SWAN) wasn’t even discovered until after perihelion, when solar heating triggered a surge in gas and dust. Both remind us that comets can surprise us in the best ways.”
When And Where To See The Comets
The best time to spot Comet Lemmon and Comet SWAN this weekend is during a 30-minute window starting about 90 minutes after sunset wherever you are. Both are visible after sunset but in opposite parts of the sky — Lemmon in the northwest and SWAN in the southwest.
Check the time of sunset where you are. For New York City, sunset is at 6:05-6:08 p.m. EDT, with the ideal viewing about 7:35–8:08 p.m. EDT.
Comet Lemmon can also be seen before dawn, though only through the weekend. Look about 90 minutes before sunrise. For New York City, sunrise is at 7:11-7:13 a.m. EDT, so the ideal window is around 5:41–6:13 a.m. EDT.
The best time to see Comet Lemmon on Oct. 17 will be 90 minutes after sunset.
Stellarium
How To Find Comet Lemmon
After sunset, look northwest. Lemmon will appear below the curved handle of the Big Dipper, roughly halfway along a line between the handle’s end star, Alkaid, and the orange star Arcturus farther west. Its height above the horizon varies, but from New York it will be around 14-17 degrees high at around 7:35 p.m. this weekend. The comet will gradually sink lower as twilight deepens each evening.
Before sunrise, look northeast. The Big Dipper’s handle will point down toward the horizon. Look to the right side of the final star in the handle, Alkaid, for a bright star called Cor Caroli. Comet Lemmon will be just below it. From New York, it will appear about 10 degrees high — roughly the span of your outstretched fist — at around 5:41 a.m. EDT this weekend. As a bonus, Venus rises at about the same time, and a delicate waning crescent moon will be also be nearby.
The best time to see Comet SWAN on Oct. 17 will be 90 minutes after sunset.
Stellarium
How To Find Comet Swan
Blueish-green Comet SWAN will be visible in binoculars low in the southwest after sunset. On Saturday, it will be in the constellation Scutum, above the famous “Teapot” asterism in Sagittarius. On Sunday, it will sit slightly higher — around 34 degrees up — and reach its closest point to Earth, shining faintly against the backdrop of the Milky Way. By Monday, Oct. 20, SWAN will drift into the constellation Aquila, just below the bright star Altair in the Summer Triangle.
From New York, the comet will appear about 31 degrees high at 7:38 p.m. on Saturday, 34 degrees on Sunday, and close to 38 degrees on Monday before gradually sinking into the southwest horizon.
Check my feed every day this month for a daily “comet tracker” with finder charts and tips for viewing Comet Lemmon and Comet SWAN.
