Now’s the time to see Comet Lemmon

Here’s the location of Comet C/2025 A6 (Lemmon) on the morning of October 17, 2025. This view shows the northeastern sky 90 minutes before sunrise for longitude 90° west and latitude 40 north°. At this time and for this location, the comet will be 16° above the horizon.
Credit: M. Zastrow/Stellarium

Key Takeaways:

• Comet C/2025 A6 (Lemmon) is currently visible in both morning and evening skies, initially located near the Big Dipper within Canes Venatici before transitioning into Boötes.
• Its perigee, the closest approach to Earth, will occur on October 21 at a distance of 28.6 million miles (46 million kilometers), coinciding with the New Moon and anticipated to be its brightest period.
• Optimal observation times are 90 minutes after sunset (facing northwest) or before sunrise (facing northeast), with specific instructions provided for both binocular and telescopic viewing.
• Discovered on January 3, 2025, by the Mount Lemmon Survey, its orbital period will decrease from approximately 1,350 years to 1,150 years after its November 8 perihelion, delaying its next appearance until around 3175.

Key takeaways sponsored by The Space Store

During the past week, you had to get up before morning twilight to spot Comet C/2025 A6 (Lemmon). And you still can. But thanks to its position in the north, now you also can see it in the evening sky. The comet is currently passing in front of the stars of the constellation Canes Venatici the Hunting Dogs. But, as both of the diagrams here show, it lies near a star pattern that’s a lot easier to find: the Big Dipper.

Comet Lemmon is inbound right now and its closest approach to Earth will occur October 21, which also just so happens to be the date of New Moon. Its minimum distance from Earth (called perigee) will be 28.6 million miles (46 million kilometers).

Fortunately, the Moon is becoming a thinner crescent in the sky with each passing day. Plus, it’s only visible in the morning before sunrise, which means the evening sky is free of its light.

Observe it

First, find the time the Sun rises and sets at your location. A quick Google search for, “When is sunrise and sunset at [location]” will do it. Then, head out an hour and a half earlier than your sunrise time — or an hour and a half later than your sunset time. In the morning, you’ll need to face northeast; in the evening, northwest. Use the finder charts here to identify some of the visible stars, and then point binoculars toward the comet’s location and try to see it.

Comet Lemmon will move into the constellation Boötes the Herdsman on the 20th. One day later — at perigee — the comet will lie less than 2° southwest of the magnitude 3.6 star Rho Boötis. Its minimum distance from Earth will be 28.6 million miles (46 million kilometers). Weather permitting, the morning and evening of the 21st will be when Comet Lemmon looks its brightest because that’s when it will be closest to us. But comets sometimes perform erratically, so observe it several days before and several days after perigee, just in case.

If you’re using a telescope to observe it, set your instrument outside about an hour before you plan to use it to let it adjust to the ambient temperature. Start viewing Comet Lemmon with your lowest power eyepiece. Depending on the length of the tail, you might be able to see the whole comet. Then, step by step, increase the magnification and scan the comet’s length for details. Can you see a single tail, or are there two? Are any parts of the tail brighter than others? Does the tail look disconnected at any point? Take your time.

More details

Comet Lemmon was discovered January 3, 2025, as part of the Mount Lemmon Survey, which uses a 60-inch telescope at Mt. Lemmon, Arizona (a scant 15.5 miles north of the author’s home). The camera attached to the telescope’s prime focus captures images that are 5° square.

Interestingly, the comet’s current orbital period is approximately 1,350 years. But after its perihelion passage (its closest approach to the Sun) on November 8, our star’s gravity will reduce that to 1,150 years. So, the next chance for earthbound observers to see this occasional visitor will be around the year 3175.

So, take a few minutes in the morning or evening (or both!) to spot Comet Lemmon — a ball of frozen gases currently speeding past Earth at 135,000 miles per hour (217,000 kilometers per hour). Don’t wait too long because the comet will start to fade after the 21st. Plus, the Moon will reenter the evening sky after that date. Now is the time. Good luck!