If you haven’t had the opportunity to witness the stunning green comets yet, mark your calendar for Sunday, October 26. This date offers your final chance to observe both the brighter Comet Lemmon (C/2025 A6) and the fainter Comet SWAN (C/2025 R2), as they rapidly move away from Earth, causing their brightness to diminish. With a 24%-lit waxing crescent moon approaching, viewing conditions will soon become more challenging. Comet Lemmon will be positioned in the northwestern sky, while Comet SWAN will be located below the Summer Triangle stars in the southern sky, near Saturn. Grab your binoculars and prepare for a celestial experience that won’t come around again for 1,150 years.
The optimal time to observe Comet Lemmon and Comet SWAN on October 26 is during a 30-minute window starting approximately 90 minutes after sunset in your location. While both comets are visible after sunset, they occupy opposite sides of the sky: Lemmon in the northwest and SWAN in the southwest. For instance, in New York City, where sunset occurs at 5:56 p.m. EDT, the best viewing window is from 7:26 to 7:56 p.m. EDT. The low position of the waxing crescent moon in the southwest will set early, ensuring darker skies for optimal comet viewing.
To locate Comet Lemmon, which is currently about 56.9 million miles (91.6 million kilometers) from the sun and 59.8 million miles (96.2 million kilometers) from Earth, look towards the west after sunset on October 26. Specifically, position yourself above-left of the bright star Arcturus, which will be low on the west-northwest horizon. You can trace the arc of stars in the handle of the Big Dipper to reach Arcturus, then make a right-angle turn towards Rasalhague, the brightest star in the constellation Ophiuchus. Comet Lemmon will be directly beneath the bright star Vega, appearing approximately 21 degrees above the horizon from New York at 7:26 p.m. EDT, gradually sinking as twilight deepens.
Comet SWAN, located 101.2 million miles (162.9 million kilometers) from the sun and 27.8 million miles (44.8 million kilometers) from Earth, will also be visible with binoculars on October 26. Look low in the southern sky after sunset to spot SWAN, which can be found within the constellation Aquarius, positioned below and to the left of the bright star Altair in the Summer Triangle. The comet will be nestled between Altair and Fomalhaut, a bright star closer to the horizon. Depending on your location, Comet SWAN will appear around 45 degrees above the horizon when it becomes visible in New York.
For those eager to track the comets, be sure to check my feed daily throughout the month for a comet tracker featuring finder charts and tips for observing Comet Lemmon and Comet SWAN from mid-northern latitudes. Additionally, you can explore related articles on topics such as how to photograph the green comets, the best stargazing apps for comet hunting, and a list of 25 dark sky parks in the U.S. to enhance your viewing experience.
For more insights on comets and celestial events, check out these articles:
Comet Tracker For Thursday: It’s Finally Time To See Rare Twin Comets A Once-In-A-Lifetime Green Comet May Soon Be Visible, Scientists Say See Rare Sight Of Two Comets As Meteor Shower Peaks — Here’s When Comet Lemmon: Your Ultimate Viewing Guide To The ‘Comet Of The Year’ Two Naked Eye Comets, ‘Harvest Moon’ And Fireballs: October’s Night Sky Orionid Meteor Shower Begins Thursday — When To See It At Its Best With Two Comets