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 evening object for northern observers, visible just west of Boötes, having passed beneath the handle of the Big Dipper / Plough and heading towards Arcturus.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 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.
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…
Below is our blog on the comet, detailing what we've found while we've been out observing it.
We'll keep this blog updated with a new section each time we get a chance to observe it.
Scroll further down for past entries in the blog.
Late October
I've been observing comet Lemmon from Kielder, one of the darkest places in England, to see if I can get a better view.
Find out how I got on in my report on observing comet C/2025 A6 (LEMMON) from Kielder.
The comet, which passed closest to the Earth on 21 October 2025, is now between around magnitude +3 and +4.
It's a naked-eye object from dark sky locations, visible in the evening sky as a smudgy, elongated mist patch to the upper left of the bright star Arcturus.
It is a quite beautiful sight in binoculars, with a prominent tail several degrees in lengthy pushing away from its bright, star-like head.
In a small telescope under low magnification it is a striking sight, its starry nucleus surrounded by a hazy cloud of dust and gas.
Its tail stretches out right across and then beyond the field of view.
Under higher magnifications, subtle structure can be seen close to the head, jets, plumes and shells of material that show how active the comet's icy nucleus has become.
Photographically, the comet is a wonderful target. It is bright enough to be picked up by the cameras on modern smartphones set to Night mode (or equivalent), but only as a very small elongated smudge, without much detail.
Photographers taking single long exposures with tripod-mounted DSLRs and wide angle lenses are capturing beautiful images showing the comet's long, blue ion tail stretching for ten degrees or more.
Tracked-and-stacked images taken with longer lenses are capturing fascinating detail in the tail, narrow ribbons and streamers embedded within it and knots and clumps of material moving down it.
In terms of photographer, comet C/2025 A6 Lemmon is the best comet for a long time.
I'm currently up at Kielder in Northumberland, one of the darkest places in the UK, and on the night of 23 October, the comet was clearly visible to the naked eye under the beautiful starry sky.
In my 8-inch Dobsonian telescope it was a fascinating sight, its smoky tail filling the eyepiece.
Through binoculars its tail looked like a short length of airplane contrail, glowing with a misty grey-blue hue.
But the best views came through my Seestar S50 smart telescope, which picked up dramatic changes in the appearance and structure of the tail in images taken just minutes apart.
The comet is now moving away from Earth but will be observable in the evening sky for some time yet.
To find it, go out around an hour after sunset, find the bright star Arcturus shining low in the west, then look up to around the ten o'clock position from it.
The comet will be there, a small smudge perhaps as far away from Arcturus as your little finger held out at arm's length.
If you don't see it with just your eyes, scan that area of the sky with your binoculars and it will pop into view.
The Moon will start to interfere with the comet soon, so any chance you get over the next few nights do get out there and look for Comet Lemmon.
It won't be back this way again for a long time...
Mid October
For many weeks now, comet observers in the northern hemisphere wanting to see Comet C/2025 A6 (LEMMON) have had to set our phone or bedside alarms for you’re-having-a-laugh-o’clock in the morning, because it has only been visible in the hours before sunrise.
But good news for all of the sleep-deprived comet-hunters: I can personally confirm that Comet A6 (Lemmon) is now visible in the evening sky from mid-northern latitudes too!
I know this because I went out on 9 October hoping, but not expecting, to image the comet with my Seestar smart telescope and see it through my binoculars from the park across the road from where I live.
I was totally prepared to fail completely, because I knew everything would be against me: the northwest sky would still be quite bright after sunset… an almost Full Moon would be rising off to the comet’s right… Kendal’s light pollution is so bad that it could double as Los Angeles in a Bladerunner film…
And the comet itself would be very low in the sky, scraping the tops of the trees and roofs around the park. But I had to try –
And there it was in the very first test image I took with my Seestar five minutes after setting it up: a surprisingly bright green-white smudged star with a faint mistiness stretching off to its right – the comet’s tail, overwhelmed somewhat by the bright sky.
I scanned the sky beneath the bowl of The Big Dipper with my binocs but I couldn’t see the comet because of the light pollution and moonlight. But that would have been a bonus.
For the next hour or so I took images of the comet with my Seestar, hoping to catch details in the tail, but after stacking them they’re just not there.
The sky was just too bright from light pollution and moonlight.
But as poor as my images are, they are enough to make me feel pretty sure that once that Moon has moved out of the way, Comet A6 Lemmon will be faintly visible to the naked eye as a tiny smudge from places with very dark skies, and easily visible in binocs from elsewhere.
So, if you haven’t seen this comet yet because it would have meant getting up before sunrise, you can now see it in the evening sky, beneath the stars of the Big Dipper, moving slowly but steadily westwards towards Arcturus.
The Moon is spoiling the view at the moment, but when it’s gone I think we might be in for a treat.
Early October
Observing comets is never easy. They’re often only visible for a short time after sunset or before sunrise, and even then most of the ones that make it up out of the twilight into a darker sky are fainter and fuzzier than even the faintest and fuzziest deep sky objects.
But observing Comet C/2025 A6 (LEMMON) from the UK is proving almost impossible at the moment, as one foul weather system after another barrels over us.
Seriously, I am sure they have better stargazing weather on Venus, or in Mordor.
Luckily, observers in other parts of the world have been enjoying much clearer skies, and enjoying great views of the comet too, so we can keep up to date with the development of this celestial visitor.
The comet is now reportedly shining at around 7th magnitude, but some observers blessed with very dark skies place have estimated it is now almost 6th magnitude.
That would mean it is nudging naked-eye visibility, but for now it remains a target for visual observers using binoculars and telescopes, and imagers using photographic and equipment that allows them to take tracked, long exposure images of the sky.
Observers using binoculars and small telescopes have reported seeing the tail through them quite easily.
Most imagers are picking up at least a few degrees of tail, as are the users of Smart telescopes, but the very best images, taken from desert locations with some of the best 'amateur' equipment available, reveal a long, thin tail – with many distinct braids and streamers running through it – which can be measured out to an impressive length of 12 degrees.
Hopefully that’s a good sign for its future development.
Will A6 become visible to the naked eye? Well, without a time machine to whisk us forwards in time a few weeks we still can’t possibly know that, but if it keeps brightening as it has been doing it is on track to reach 3rd magnitude at the end of October, maybe even +2.5.
That would make it quite easily visible to the naked eye for those blessed with good eyesight and dark, light pollution-free skies, and easily visible through binoculars and telescopes for the rest of us who maybe aren’t quite so lucky.
While we don’t know exactly what it will look like, how bright it will be or how long its tail will be in the weeks ahead, we do know where it will be in the sky.
Over the next couple of weeks the comet will drift eastwards beneath the stars of the Big Dipper/The Plough, that most famous asterism of all which lies within Ursa Major.
It will be best seen in the evening sky from mid-October, when it will be found quite low in the north-west as the sky darkens after sunset.
It will then be moving beneath the curved handle of the Big Dipper/The Plough, heading eastwards towards the bright star Arcturus, which it will pass some distance above on 22/23 October.
After that stellar close encounter it will continue tracking eastwards, dipping down beneath Corona Borealis.
By the time it reaches its closest point to the Sun – perihelion - on 8 November, Comet A6 Lemmon will be dropping through southern Ophiuchus, already low in the south-west at sunset and setting only a couple of hours later.
Hopefully by then we’ll all have at least a few very happy memories of seeing it in the sky with our naked eyes. We’ll just have to wait and see.
For now, Comet A6 Lemmon is definitely looking very promising, and is already delighting observers with skies clear enough to see it.
Get out and see it if you get a chance!
Late September
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…
