Comet observers are rather spoiled at the moment.
Not only is there a comet from an entirely different part of the Galaxy racing through our Solar System (comet 3I/ATLAS, the one online conspiracy theorists are claiming is an alien spaceship – spoiler alert: it’s not), but there is a brightening ‘family member’ comet visible in the sky too.
Comet C/2025 A6 (LEMMON) is an early morning object for northern observers, drifting slowly through the constellation of Lynx, roughly halfway between brilliant Jupiter and the stars of the Plough/Big Dipper.
Here's the story so far.
Experienced comet photographers have been using their high-tech telescopes and cameras to photograph comet C/2025 A6 (LEMMON) for a couple of weeks now.
Their processed images show it's very active and dynamic, sporting a tail knotted and clotted with clumps of material.
But it's still too faint to see without help from binoculars or telescopes, and is so small in the sky it’s essentially just an out-of-focus greenish star even in those.
But although it’s not much to look at yet, comet observers monitoring its behaviour are becoming increasingly optimistic that it might be visible to the naked eye at the end of October 2025, maybe even sporting a long tail.
But before we get too carried away with mights and maybes, let’s go back a little, to the start of A6’s story.
Comet C/2025 A6 (LEMMON) discovery
C/2025 A6 (LEMMON) was discovered on 3 January 2025 by astronomer David C. Fuls as part of the Mount Lemmon Survey.
This is a near-Earth object detection program operated by the University of Arizona's Steward Observatory, using a 1.5-meter (60-inch) Cassegrain reflector telescope at Mount Lemmon Observatory in Arizona.
Back then, C/2025 A6 (LEMMON) was just a magnitude +21.5 dot of light.
Follow-up observations quickly revealed cometary activity, leading to its official designation as a comet: C/2025 A6 (Lemmon).
When scientists calculated the comet’s orbit, they found it had last visited the inner Solar System over a millennium ago, possibly during the Middle Ages...
And when A6’s numbers were crunched even further, they suggested that it would only reach about magnitude +10 when it was at its closest to the Sun.
That made it a modest target for experienced amateur observers, but nothing for anyone else to get too excited about.
So as it passed through solar conjunction on 2 July 2025, and was temporarily lost from view in the Sun’s glare, no-one really expected very much from it when it reappeared.
A brightening effect
Comets love surprising the people who observe them, and proving them wrong if possible.
And when comet C/2025 A6 (LEMMON) re-emerged into the morning sky in mid-August 2025, it was far brighter than expected, possibly due to an outburst of activity on its icy nucleus.
Comet observers began to look at it with more interest, and some even dared to raise a Spock-like eyebrow, allowing themselves to wonder if it might put on a good show at the end of October 2025, when it would be best placed for observation from Earth…
Now, as September draws to a close, many observers are becoming quite optimistic about A6’s prospects.
It's shining at around 8th or 9th magnitude and is visible in binoculars and small telescopes, though not visible with the naked eye yet.
C/2025 A6 has developed a tail, which is striking on long exposure photographs, and if it keeps brightening as it has been doing, it's on track to reach +3 magnitude at the end of October 2025.
That would make it visible to the naked eye for those blessed with good eyesight and dark, light pollution-free skies, and visible through binoculars and telescopes for others not quite so lucky.
However, some computer simulations suggest A6 might be even brighter, perhaps reaching +2 magnitude or higher, with a dust tail several degrees long and a much longer gas tail.
However, that would probably only show up clearly on photographs and not be obvious to the naked eye.
That’s obviously a very exciting prospect, but it’s important to not get carried away here.
Comets are fickle creatures, and these cosmic crystal ball predictions for A6’s future may not come true.
It is certainly not going to 'light up the sky' or 'streak across the heavens' like social media reports are already suggesting.
What we know about C/2025 A6 so far
The one thing we can currently safely say is that comet C/2025 A6 (LEMMON) is visible in the morning sky for northern observers now.
It's already bright enough to be seen as a small, fuzzy, greenish star through binoculars and small telescopes.
It can even be photographed using very basic equipment.
I was out at 02:00 in late September 2025, photographing it from a park in the middle of Kendal, Cumbria, UK using a basic Canon 700D DSLR camera tracking the sky on a motorised mount.
Despite the streetlights and security lights glaring around me, the comet showed up clearly on my images, as you can see here.
Smart telescopes such as Seestars and Dwarfs etc. will definitely pick it up without any difficulty.
For more advice, read our guide on how to photograph a comet.
As for the future, now we have to wait and see what happens.
Over the next few weeks I'll be keeping a close eye on Comet C/2025 A6 (LEMMON) and giving you the latest information about it in this ongoing blog.
I'll help you find it in the sky and keep you updated on how bright it gets – or doesn’t get.
So, keep checking back here regularly to make sure you don’t miss anything.
And maybe cross your fingers too…
