Comet C/2025 A6 Lemmon – 21st Oct 2025

Comet Lemmon, or C/2025 A6 (Lemmon), was discovered by astronomers at the Mount Lemmon Survey, in Arizona, on the 3rd January 2025. 

The comet is currently low in the northwestern sky after nightfall in the constellation of Boötes, not far from the bright star Arcturus. 

On the 24th Oct it will still be above Arcturus but near the star Izar. (Note: The handle of the Big Dipper points towards Arcturus.), and in the coming days it will move into the constellation Serpens.

Sky chart showing the location of C/2025 A6 (Lemmon) at the end of October 2025. Credit: Astronomy Now magazine.

On the evening of the 21st Oct 2025, several CMHASD members managed to image the comet quickly through a gap in the clouds or with a thin veil of cloud.

CMHASD member George Buckberry captured the comet at 7:40pm using his Dwarf3 smart scope. His fantastic image below is made up of only 3 stacked images at 15S, gain 60 and Astro filter. Then run through Stellar Studio and no other processing. 

The Water mark also shows NGC 5641 which was a little further West at the time George took the images of the comet.

 

Kevin Smith captured the comet also using a Dwarf3 smart scope on the 21st Oct around the same time as George. His fantastic images are below.

 

Honor Wheeler captured the comet at 7.19pm using a Canon M6II, Tamron 18-400mm, set at ISO3200, 3" and F6.3. Her superb image is below.

 

Finally member Jim Burchell captured the comet a little bit later on the 21st Oct at 20:19 BST.  Jim used a Pentax KP set at F5.6, 20sec, 135 mm and iso 800 on a Skywatcher star adventure. His super image is below.

Comet C/2023 A3 Tsuchinshan Atlas by Jim Burchell – Oct 2024

The location of Comet C/2023 A3 Tsuchinshan-Atlas in October 2024.
Photo credit: https://www.skyatnightmagazine.com/advice/comet-c-2023-a3-tsuchinshan-atlas-october-2024
 
 
Below are a selection of fantastic images of Comet C/2023 A3 Tsuchinshan-Atlas taken by CMHASD member Jim Burchell taken over 6 days in October 2024.
 
Comet C/2023 A3 (Tsuchinshan-ATLAS) is a long-period comet from the Oort cloud that was discovered in 2023 by the Purple Mountain Observatory in China in January 2023 and independently by the ATLAS (Asteroid Terrestrial-impact Last Alert System) in South Africa in February 2023. It was named after both observatories.
 
18th Oct 2024
 
Image taken from Dartford top road with a Pentax KP and a 50-300 MM zoom lens at 70 mm. F5.6, 5 seconds, iso 1600, attached to a Skywacher Star Adventurer
 
19th Oct 2024
 
 
Images were taken from Otford using a Pentax KP and 50-300 mm lens attached to a Skywacher Star Adventurer. Camera settings were 300 mm, F7.1, 60 seconds and iso 800
 
 
23rd Oct 2024
 
 
Images were taken from Otford using a Pentax KP DSLR and a 50-300 mm zoom lens attached to a Skywacher Star Adventurer.  Camera settings were 300 mm, F7.1, 60 seconds and iso 800.

Comet C2023 A3 Tsuchinshan-ATLAS by Honor Wheeler – 12th Oct 2024

Four members of CMHASD; John Archer, Gary Hunt, Jo Southgate and Honor Wheeler met up at Top Dartford Road at around 18:30 to see if they could spot comet C2023 A3 Tsuchinshan - ATLAS on the 12th Oct 2024.  The rain cleared just in time and the sky was clearing of cloud as they set up. It took about 25 minutes looking but in the end they spotted the comet nucleus with a pair of 8x42 binoculars in the orange glow of the sunset i.e. in the Western sky approx 10 to 20° above the horizon :-)

Below are some fantastic images of the comet taken by Honor.  These images were also the 1st ones of the comet to be put on the British Astronomical Association (BAA) website - well done Honor!

 

Comet C/2023 A3 (Tsuchinshan–ATLAS) by member Jim Burchell – 15th May 2024

A great image capturing Comet C/2023 A3 (Tsuchinshan–ATLAS) by member Jim Burchell from Swanley. 
Jim said ''I took this image on the evening of 15th of May when the Comet was in the constellation of Virgo with my Seestar S50. As you see the Comet is showing a small tail....''

C/2023 A3 (Tsuchinshan–ATLAS) is a comet from the Oort cloud and was discovered by the Purple Mountain Observatory in China on 9 January 2023 and independently found by ATLAS South Africa on 22 February 2023.

Jim was the 1st member of CMHASD to image the comet - Well done Jim!

Image acquired using a Seestar S50: 48 X 10 second stacked images.

AstroImageJ Demonstration

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We had an informal meeting over Christmas where Martin took the members through using AstroImageJ (AIJ) he covered the following...

  • Loading an image
  • analysing stars in an image
  • plate solving an image
  • batch processing images to calibrate them
  •  aligning and stacking images
  • photometry on a sequence of images

[caption id="" align="aligncenter" width="800"]MartinExplaininghow-to-us-astroimagej Martin Demonstrating AstroImageJ[/caption]

Final image.

[caption id="" align="aligncenter" width="670"]C2017T2_20191201_2149 Comet C/2017 T2 20191201 21:49 Simon Dawes[/caption]

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Comet panSTARRS c/2011 L4

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We will be attempting to observe Comet PanSTARRS C/2011 L4 on the 12th March 2013 at the Pavilion. The comet will be 11 degrees above the horizon at 19:00, close to Uranus; the Sun - according to StaryNight pro 4.5 sets at 19:00 so we will want to set up any equipment before sunset.

This will be a challenging observation, the comet is predicted to be close to its brightest but it will be in bright twilight
CAUTION SUN MUST HAVE SET BEFORE YOU USE YOUR BINOCULARS

panstarrsC-2011_L4

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Stack of 33 images ED80 Canon 600D

Image by Martin Crow

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30s exposure Canon 650D Comet is just below centre of image. Image taken at the BAA Winchester Weekend.

Image by Simon Dawes

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CMHASDCalender2014.09ArthurCockburn_September

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2013-03-14 Just south of Cahors in France. 200mm lens f5.6 1s exposure ISO 1250

Image by Arthur Cockburn

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