My picture of Comet C/2025 A6 Lemmon in Magazine Heelal

My image of Comet C/2025 A6 Lemmon is published in Magazine Heelal. This is my 35th contribution to this Astronomical magazine. 

 

Interstellar Comet 3I/ATLAS

Comet 3I/ATLAS or C/2025 N1 (ATLAS) is the third known object from outside our solar system to be discovered passing through our celestial neighborhood. Astronomers have categorized this object as interstellar because of the hyperbolic shape of its orbital path. (It does not follow a closed orbital path about the Sun.) When the orbit of 3I/ATLAS is traced into the past, the comet clearly originates from outside our solar system.
As of 2025, three interstellar objects have been discovered traveling through the Solar System:
1I/ʻOumuamua in 2017, 2I/Borisov in 2019, and 3I/ATLAS in 2025. The prefix "1I" identifies the object as the first confirmed interstellar interloper, "2I" as the second, and so on.



This morning was the first morning with a clear sky. I used my DSLR Nikon D7500 with a zoom lens to image the comet in constellation Leo. It was not easy with the moon almost 60° illuminated.


Setting: Nikon D7500 with zoomlens.
No Guiding and no cable (as it was broken the night before).
Software: APP, ASTAP, CS4, DeNoise AI, Stellarium, SkySaferi.


Workproces: stacking 7 images with APP each ISO6400 4s. The picture was edited using APP tools light pollution and background calibration. Next, ASTAP was used to extract the green channel and Denoise AI to remove noise. This noise free image was again uploaded in ASTAP and star annotation was set. Unknown star annotation identified the position of the comet. This on the "same" location as found in Stellarium and SkySafari.

Comet C/2025 A6 (Lemmon) Nov 2 and ASTAP

November 2nd, 2025, both transparancy and seeing bad. So, no good images of Comet C/2025 A6 (Lemmon). Images stacked using APP and ASTAP. ASTAP was used to identify some object like Messier M10 & M12 aswell as two Asteroids. 

Setting: Nikon D7500 on Skywatchter Star Adventurer 2i

Software : APP, ASTAP, CS4 and DeNoise AI

Comet C/2025 A6 Lemmon

Open sky but a lot of dew resulting in moderate images of Comet C/2025 A6 (Lemmon).

Using ASTAP, area magnitude is 5,4... cool!

Comet C/2025 A6 Lemmon on Halloween evening

Haloween evening, October 31, 2025 during a bright interval I was able to image Comet C/2025 A6 (Lemmon).
This time I used my Star Adventurer 2i together with Nikon D7500, a set up which made it possible to track the comet for 60s.

Setting: Nikon D7500

Mount: Skywatcher Star Adventurer 2i

Exposure : 4x60s ISO800; 2x10s ISO3200; 2x10s ISO6400

Software: APP, CS4 and DeNoise AI

Comet C/2025 A6 (Lemmon) October 27

On the evening of October 27 ... a cloud free sky. So time to observe Comet C/2025 A6 (Lemmon).
I took a wide field using more then 260 images, each 5s.

The other images were taken with a larger focal point but with a time difference of one hour. Due to this time difference, the comet was low above the horizon resulting in fainting out of the tail.

Comet C/2025 A6 (Lemmon)

Finally an open sky for about half and hour, which was enough to capture comet C/2025 A6 (Lemmon).

Setting: Nikon D7500 with 112mm f/5.3, ISO6400 and exposure time of 5s

No Guiding

Software: APP 2.0.0. beta29, DeNoise AI, CS4

APP: Normal and MAD regression Avg (8;2)

Discussion:

Brigth core with both dust tail and ion tail. Structure in ion tail with knots aswell with small and wider regions. Tail extends minimum 5° .

Comet C/2025 A6 (Lemmon)

This morning I took some images of Comet C/2025 A6 (Lemmon). The comet is currently 1,1AU away from Earth and will be at closest on October 21, 2025 on a distance of 0,59AU. Perihelion transit will take place on November 8th. Max brightness is predicted between these two days with the Comet low above the horizon after sunset.

Setting: Nikon D7500 f/4 28mm ISO3200 4s.
Editing: CS4 and DeNoise AI

Comet 12P/Pons-Brooks in Big Bend (Texas)

My Helios colleague Lieven asked my why comet 12P/Pons-Brooks wasn't selected in my 2024 Highlights. My answer was that I don't have good pictures of the Comet. But then I realised that I tried to image the Comet when I was in Big Bend (Texas) a couple of days after the Solar Eclipse of April 8th, 2024. With the support from Stellarium I good trace the Comet on my images, including Uranus.

Comet C/2023 A3 Tsuchinshan-Atlas reworked APP

I reworked my images of Comet C/2023 A3 Tsuchinshan-Atlas using APP v2.0.0 beta 29 with MAD setting.

Settings APP:

Integrate : Median

Filter MAD rejection

Kappa Low: 8

Kappa High: 2

Comet C/2023 A3 as seen by the STEREO-A SECCHI HI-1 coronagraph.

Comet C/2023 A3 as seen by the STEREO-A SECCHI HI-1 coronagraph. Striations can be seen in the dust tail, and interactions between the faint ion tail and the solar wind can be observed.
The solar Corona was subtracted out to show the solar wind more clearly. The contrast of the comet tail and the solar wind was enhanced with local histogram equalization.
The vertical lines above Venus on the left and the comet are saturation artefacts from the CCD sensor.

Credit: NASA / STEREO-A / SECCHI HI-1 / Simeon Schmauß
processed from the raw data: secchi.nrl.navy.mil/postflight/hi_1/L0/a/img/20241004/

Click on picture to start video

My input: these images show aswell how to interpret the antitail of the comet.

Compilation video of Comet C/2023 A3 Tsuchinshan-Atlas

I made a video of my best images of Comet C/2023 A3 Tsuchinshan-ATLAS. Click on the picture below to start the video; video is best seen on your PC

Comet C/2023 A3 Tsuchinshan Atlas October 25

A combination of clear and cloudy skies. I did set up my Star Adventurer 2i with Nikon D7500 but Snap connection failed again. I really need to solve this .. maybe getting a complete new snap connector. 

Next to this I set up my EQAZ6 with TLAPO80/480 and ASI2600. Polar allignement was "excellent" and I used sharpcap to capture images. Increasing the exposure time resulted in an error. Switching over to N.I.N.A. wasn't successful either. Finally, I switched over to ASIStudio and found out that ASI2600 power was disconnected. I could fix this but in the meantime the Comet was about 5° above the horizon. 

Some images shot are posted below; I'm still seeing the a faint anti-tail, the huge dusttail but no plasmatail. I made some images using my OIII filter; no more details vissible. 

Comet C/2023 A3 Tsuchinshan Atlas October 22

Clouds dissapeared for a half hour, enough to take some images of comet C/2023 A3 TsushinShan Atlas. The comet still has a anti-tail but under a bigger angle.

Image were taken with Nikon D7500 on my Star Adventurer 2i mount. Total integration time was 340s (17x20s).

Stacking was done using APP and final editing with CS4 en DeNoise AI.

Comet C/2023 A3 Tsuchinshan-Atlas stacked with APP 2.0.0. beta 29

I reworked my images of the Comet C/2023 A3 Tsuchinshan Atlas using the beta 29 version of APP 2.0.0.

 

Comet A3 Tsuchinshan Atlas Stacked

Stacking of 23 images with APP. The anti-tail is becoming more visible after stacking.

Comet C/2023 A3 Tsuchinshan Atlas with anti tail

Yesterday evening I planned my trip after investigating the weather forecast using different models. Only two of the models forecasted the same weather : alaro and meteoblue. West of Brussels was the best chance of having a clear sky. This morning weather forecast changed but at noon conditions became better again. So I took my chance a drove to Denderleeuw were I met with my colleague Walter. After a drink and a small snack we drove south towards Nederhasselt, near Ninove. 

In an open field with a 270° view and no clouds this was our chance to see Comet C/2023 Tsuchinshan Atlas. Only at UT17h43 we could spot the comet using my camera. As from then, it went better and better and we were able to see the comet with the naked eye and a tail of 20°. Using the camera the anti tail was visible aswell. 

It was worth doing the trip and both were very satisfied!

Comet 12P/Pons Brooks

Finally, I was able to set up my EQAZ6 mount to capture the Comet 12P/Pons Brooks. Unfortunately a lot of clouds but I could use 3 pictures of each 60s exposure time.

Setting: TLAPO80/480 f/6 with ASI2600MC

Filter: Optolong L-Pro

Lights: 3x60s

Software: SharpCap 4.1, APP, CS4

150.000 Visitors and Comet 12P/Pons Brooks

 

Celebrating 150.000 visitors since the start of my blog and I'm doing this with my picture I took this evening of Comet 12P/Pons Brooks.

Setting: TLAPO80/480 f/6 with Nikon D7500

Filter:Optolong L-Pro

Mount: Manfrotto

Exposure : ISO16000, 2x2s

Software: DNG converter and CS4

Comet 12P/Pons Brooks with telelens

 

Image of Comet 12P/Pons-Brooks taken on Wednesday March 27. Some high clouds but still, when looking good you will recognize two tails.

Setting: Nikon D7500 f/5.6 200mm telelens, 39x2s on ISO12500. High ISO to prevent startrailing.
Stacking was done with APP 2.0.0 beta version 26. It took some time as settings were not correct.