Interstellar Object 3I/ATLAS - C/2025 N1 (ATLAS)

[Pierre_C]

Originally Posted by Dennis

In my experience with faint moving objects such as Near Earth Asteroids, I have found that for those that are fast moving, I cannot record anything fainter than around mag 16 to 16.5 as they do not register on the sensor. This is through my Mewlon 210 or C9.25 OTA’s...

Thanks, Dennis.

With my basic equipment, I think I will wait for August when it will still be high in the sky and possibly around magnitude 14.

[Dennis]

Originally Posted by Pierre_C

Thanks, Dennis.

With my basic equipment, I think I will wait for August when it will still be high in the sky and possibly around magnitude 14.

Hi Pierre

I’ve not used my gear much recently and so when I set up for this Solar System Interloper, I found several applications, drivers and firmware that were outdated and needed to be updated. In the field is not the best place to do this!

I really should have set up and performed a few dry runs first, just to check the HW/SW status and refresh my set up and operation skills.

So, if you have the time and the conditions, definitely have a go before the big night, just to make sure that everything runs as smoothly as possible when the comet is within reach.

Good luck.

Dennis

[Pierre_C]

Originally Posted by Dennis

... So, if you have the time and the conditions, definitely have a go before the big night, just to make sure that everything runs as smoothly as possible when the comet is within reach...

Thanks for the great advice, Dennis.

I am currently writing up some personal notes to practice on 3 Juno and 4 Vesta (at magnitudes 5-7); and then 230 Athamantis, 23 Thalia and 115 Thyra (at magnitudes 10-11). That will give me a sense of whether I will be able to capture 3I/ATLAS at around magnitude 14 and moving at around 3 times as fast in August.

[Dennis]

Here is a 30x60 sec exposure of Comet C/2025 N1 (ATLAS) taken with a Celestron 11 Edge HD at F10 from our backyard in Brisbane.

I downloaded an Ephemeris for 19th July for our back garden and imported it into The Sky X Pro as a custom database (SDB) which plotted the position in TSX.

TSX reports the comet as 16.98 mag based on the JPL Horizons data.

Celestron 11 Edge HD at F10
ASI 2600 MM Duo
Paramount MX+
30x60 sec exposures.
The 1st image is a full res 1280x960 crop around the comet trail.
The 2nd image has been inverted
The 3rd image has been up sampled by x2.

From TSX for the full FOV:
******** ASTROMETRIC SOLUTION RESULTS ********
Center RA (2000.0): 17h 25m 14.53s
Center Dec (2000.0): -18° 13' 35.3"
Scale: 0.5470 arcseconds/pixel
Size (pixels): 3124 x 2088
Angular Size: 0° 28' 29" x 0° 19' 02"
Position Angle: 0° 16' from north through east
Number of Stars Used in Solution: 1000 (100%)
FWHM: 4.59 pixels, 2.51 arcseconds
*********************************** ************
Dennis

[Pierre_C]

Good one, Dennis.

I can see that your images are getting sharper each time.

(I am still practicing...)

[Dennis]

Thanks Pierre, it has increased in brightness and I was able to image with the comet higher in the skies.

Cheers

Dennis

Originally Posted by Pierre_C

Good one, Dennis.

I can see that your images are getting sharper each time.

(I am still practicing...)

[middy]

After failed attempts on 2 other nights, this was my final chance before trees became a problem. Third time lucky.

This is 43 x 60 sec exposures at gain 300 with the ASI2600MC
Darks and Flats corrected
Stacked in ASTAP, aligning on the comet.

[Dennis]

Originally Posted by middy

After failed attempts on 2 other nights, this was my final chance before trees became a problem. Third time lucky.

This is 43 x 60 sec exposures at gain 300 with the ASI2600MC
Darks and Flats corrected
Stacked in ASTAP, aligning on the comet.

Nice work Andrew, it is a tricky object to find and image.

Dennis.

[Dennis]

I managed to grab 150 x 60 sec exposures, both E and W of the Meridian, hence a gap in the trail, along with those gaps that interrupted the captures due to the need to re-focus periodically.

C11 at F10.
ASI 2600 MM Pro.
150 x 60 sec exposures.

#1 is the FOV (inverted) down sampled to 1280 pix.
#2 is a full res crop 1280x960 pix around the trail

Dennis.

EDIT:
I just added Image #3, a full res 1600x1200 crop from a single, unprocessed frame opened in CCDStack, showing the comet.

Celestron C11 Edge HD at F10.
ASI 2600 MM Duo.
Single 60 sec exposure.

[Pierre_C]

Wow - that first image is so sharp.

With JPL Horizons predicting magnitude 16-17 through August, I think imaging this one will be beyond my capabilities for now.

[Dennis]

On 30th July 2025 I managed to grab several sets of images of Interstellar Comet C/2025 N1 (ATLAS).

Here is a 4-Panel composite of C/2025 N1 (ATLAS) centred on the comet using Tycho Tracker along with a full res 1280x960 pixel crop of a single unprocessed frame from one of the sets.

I had 4 sets of images, x1 set E of the Meridian and x3 sets W of the Meridian.

I used Tycho to blink through each set and only selected those contiguous frames where the comet did not impinge upon a bright field star. I then generated the track in Tycho and saved each result as a FITs file.

After converting and importing into Photoshop, I cropped the region around the comet and up sampled it x2 to generate x4 off 640x480 pixel images, which I assembled as this composite.

The Sky X Pro reported an image scale of 0.5630 arcseconds/pixel.
The Tycho Image Evaluation Graph showed FWHM values ranging from 2.13 to 3.43.

Do these results show the nucleus and coma? I don’t know.

Dennis.