What is the best time and general location to see Comets Lemmon and SWAN on Thursday, Oct. 23, 2025?

On Oct 23, observers at mid-northern latitudes will see both comets after sunset, with roughly a 90-minute window centered around 7:30–8:00 p.m. local time being optimal; Lemmon appears low in the northwest, SWAN in the southwest. Binoculars aid detection of faint tails, and darkness away from light pollution improves contrast.

Which comet is brighter and how should each be observed in terms of visibility and equipment?

Comet Lemmon (C/2025 A6) is brighter, near magnitude +4.4, and is the easier target to spot low in the northwest after sunset. Comet SWAN (C/2025 R2) is bluish-green and visible with binoculars in the southwest under Altair. Binoculars or a small telescope reveal tails; dark skies away from light pollution provide best contrast.

How can observers locate Comet Lemmon after sunset?

After sunset, look low in the northwest near the bright star Arcturus. Follow the curve of the Big Dipper’s handle toward Arcturus, then move a couple of degrees above Arcturus toward Izar. Comet Lemmon will be a few degrees to the right of Izar. Distances: Sun about 60.3 million miles away and Earth about 56.3 million miles away; in New York around 7:30 p.m. EDT it sits roughly 20° above the horizon.

How can observers locate Comet SWAN after sunset?

Comet SWAN will sit low in the south after sunset in Aquila, directly below Altair and above the Sagittarius Teapot asterism. From New York it will appear about 41 degrees above the horizon. Binoculars help reveal its bluish-green coma and tail, and a dark, clear sky improves visibility.

Comet Tracker: Where to See the Comets on Thursday, Oct. 23, 2025

Space By James Lawson Nov 12, 2025 08:52

Comets Lemmon (C/2025 A6) and SWAN (C/2025 R2) are visible after sunset in the Northern Hemisphere on Oct. 23, 2025. Binoculars will help reveal their tails; this is a last good viewing window before they fade and moonlight brightens the sky.

Two comets are relatively easy to locate in the evening sky for mid-northern latitude observers on Thursday, Oct. 23, 2025. Comet Lemmon (C/2025 A6) is the brighter of the pair and appears low in the northwest after sunset; Comet SWAN (C/2025 R2) is visible in the southwest beneath the bright star Altair. Conditions will become less favorable in the coming days as both comets recede from Earth and as the waxing crescent moon brightens the sky.

Key facts

Best viewing window: about 90 minutes after local sunset for roughly 30 minutes.
Comet Lemmon (C/2025 A6) is near magnitude +4.4 and is the easier target.
Comet SWAN (C/2025 R2) appears bluish-green and is visible with binoculars.
Binoculars or a small telescope are recommended to see comet tails; dark skies far from light pollution provide the best views.

When and where to look

Both comets are visible after sunset but in opposite parts of the sky. Look about 90 minutes after local sunset for the best opportunity; the usable window is relatively short as twilight deepens. Example: in New York City (sunset ~6:00 p.m. EDT on Oct. 23), the ideal viewing time is roughly 7:30–8:00 p.m. EDT.

How to find Comet Lemmon (C/2025 A6)

Distance from the sun: 60.3 million miles (97.1 million kilometers).
Distance from Earth: 56.3 million miles (90.5 million kilometers).

After sunset, look low in the northwest near the bright star Arcturus. Follow the curve of the Big Dipper’s handle toward Arcturus, then move a couple of degrees above Arcturus toward the star Izar. Comet Lemmon will be a few degrees to the right of Izar. From New York at about 7:30 p.m. EDT on Oct. 23 the comet will be roughly 20 degrees above the northwest horizon and will sink as the evening progresses.

Finder-guide illustration for Comet Lemmon in the northwest after sunset.

How to find Comet SWAN (C/2025 R2)

Distance from the sun: 96.5 million miles (155.3 million kilometers).
Distance from Earth: 25.5 million miles (41 million kilometers).

Comet SWAN will sit low in the south after sunset, in the constellation Aquila. It will be directly below the bright star Altair in the Summer Triangle and above the Sagittarius "Teapot" asterism. From New York the comet will appear relatively high, about 41 degrees above the horizon as it becomes visible.

Finder-guide illustration for Comet SWAN in the southwest after sunset.

Observing tips

Use binoculars to make the comets and their tails easier to see; a small telescope can reveal more detail.
Seek a dark location away from skyglow; higher altitude and clear, dry air improve visibility.
Stargazing apps or planetarium software that show the night sky for your location can help locate the comets precisely.
Expect the comets to dim in the coming days as they move away from Earth; moonlight from a waxing crescent will also reduce contrast later in the week.

Additional note: interstellar visitor

There is also an interstellar object in the inner solar system, designated 3I/ATLAS. It is much fainter and tougher to see, but notable because it originated outside the solar system and is moving at very high speed through the system.

Clear skies and modest optical aids will increase your chances of spotting the comets during the brief evening window on Oct. 23.

James Lawson

Investigative science and tech reporter focusing on AI, space industry and quantum breakthroughs

University College London (UCL) • United Kingdom