Ne Interstellar Comet 3I/ATLAS

[theskyhound]

A new interstellar comet has just been discovered, 3I/ATLAS. I have added it to the July current comets list for all versions of SkyTools. It is currently magnitude 18.5.

[PMSchu]

Thanks Greg.

ST4 predicts it'll be visible in November 2025, but we have garbage weather then.

Phil S.

[theskyhound]

Its too soon to say what its visibility will be, Phil. Its a comet, its still far from the sun and could "turn on", we don't have a long history of observations to build on, and its interstellar in origin. So hang on.

[PMSchu]

Just trying to be optimistic  .

Phil S.

[Dennis]

Hi Folks

I dusted the cobwebs off my gear and managed to grab some images of C 2025 N1 (ATLAS) from our back garden in Brisbane on Wed 30th July 2025.

I managed to grab a total of 150 x 60 sec exposures in 5x30 image segments, due to interruptions in imaging for the need to periodically re-focus and a Meridian flip. Hence the gaps in the trail.

ST4 had the comet at mag 17.01 in the constellation of Ophiuchus, whilst also providing an estimate of the Coma Diameter at 15".

The planetarium app for my Paramount MX+ could not import and compute the orbital elements of this comet (orbit too eccentric I think) whereas ST4 was able to do this, placing it bang on target.

Celestron C11 Edge HD at F10, fl=2800mm.
Camera was the ASI 2600 MM Pro.
150 x 60 sec exposures.

#1 is the FOV down sampled to 1600 pix.
#2 is a full res 1600 pix. crop around the trail

Center RA (2000.0): 16h 55m 46.29s
Center Dec (2000.0): -17° 37' 09.4"
Scale: 0.5630 arcseconds/pixel
Size (pixels): 3000 x 2000
Angular Size: 0° 29' 19" x 0° 19' 36"
Position Angle: 179° 47' from north through east
FWHM: 3.67 pixels, 2.06 arcseconds

Dennis.

3000x2000 pixel FOV downsampled to 1600 pix.
   

Full res 1600x1200 pix crop from centre of frame.
   

[PMSchu]

Hi Dennis,

Good to hear from you again. That's a very nice image you've got there. The comet is easy to see at 17 magnitude with only a 60 sec exposure.

Thanks,

Phil S.

[Dennis]

Hi Dennis,

Good to hear from you again. That's a very nice image you've got there. The comet is easy to see at 17 magnitude with only a 60 sec exposure.

Thanks,

Phil S.

Thanks Phil, we’ve had a cloudy few weeks down under which is unusual for our winters in Brisbane.

This is C/2025 N1 (ATLAS) as recorded from Brisbane on 16th August 2025.

I processed a stack of 19x60 sec frames in Tycho Tracker and then up-sampled the cropped region by x2 in Photoshop using an AI based re-sizer (ON1).

There is “fuzziness” around the comet, but I am uncertain if this is the coma, a stacking artefact or just “drift” as these were 60 sec unguided frames at 2800mm focal length.

The “fuzziness” extends for approx. 9x9 arc secs and does not appear to be elongated like the classical tail.

Dennis.

Center RA (2000.0): 16h 09m 25.48s
Center Dec (2000.0): -16° 10' 11.2"
Scale: 0.5520 arcseconds/pixel
Position Angle: 180° 12' from north through east

   

   
FWHM: 3.41 pixels, 1.88 arcseconds

[PMSchu]

The center of the comet looks larger than the star images - nonstellar, too. It definitely has a fuzzy look to it, but no telling if its a processing artifact. The star trails don't exhibit any fuzzyness.

That's another great image.

Phil S.

[theskyhound]

The center of the comet looks larger than the star images - nonstellar, too. It definitely has a fuzzy look to it, but no telling if its a processing artifact. The star trails don't exhibit any fuzzyness.

That's another great image.

Phil S.

What Phil said! Very nice images.

[theskyhound]

Hi Dennis,

Good to hear from you again. That's a very nice image you've got there. The comet is easy to see at 17 magnitude with only a 60 sec exposure.

Thanks,

Phil S.

Thanks Phil, we’ve had a cloudy few weeks down under which is unusual for our winters in Brisbane.

This is C/2025 N1 (ATLAS) as recorded from Brisbane on 16th August 2025.

I processed a stack of 19x60 sec frames in Tycho Tracker and then up-sampled the cropped region by x2 in Photoshop using an AI based re-sizer (ON1).

There is “fuzziness” around the comet, but I am uncertain if this is the coma, a stacking artefact or just “drift” as these were 60 sec unguided frames at 2800mm focal length.

The “fuzziness” extends for approx. 9x9 arc secs and does not appear to be elongated like the classical tail.

Dennis.

Center RA (2000.0): 16h 09m 25.48s
Center Dec (2000.0): -16° 10' 11.2"
Scale: 0.5520 arcseconds/pixel
Position Angle: 180° 12' from north through east




FWHM: 3.41 pixels, 1.88 arcseconds

Hi Dennis,

May I used your images on my Comet Chasing youtube channel. I will attribute.