Ne Interstellar Comet 3I/ATLAS

[Dennis]

Sure thing Greg, always happy to help with promoting the hobby and the work you do.

Dennis.

[Dennis]

Here is an image of the comet as stacked in Tycho Tracker when it was in Ophiuchus on 11th July.
 
This one was 2 sets of 30x60 sec exposures from our back garden in Brisbane.

C11 Edge HD F10 at 2800mm fl, ASI2600MM camera.
 
Dennis

   

   

[PMSchu]

Hi Dennis,

Looks like you tracked it through a star cluster. That's a lot of background stars in the field.

Again, great image!

Tycho Tracker does a nice job on your subs.

Phil S.

[Dennis]

Hi Dennis,

Looks like you tracked it through a star cluster. That's a lot of background stars in the field.

Again, great image!

Tycho Tracker does a nice job on your subs.

Phil S.

Thanks Phil, it has taken me a few attempts to "re-learn" Tycho Tracker as it has been a long time between drinks. And yes - it is an excellent resource.

I managed to record C 2025 N1 (ATLAS) from our back garden in Brisbane on 27th August 2025.

I processed the set of frames in Tycho Tracker and here are the Tracked (aligned on Comet) and Trailed (aligned on stars) Views as generated from within Tycho Tracker.

Celestron C11 Edge HD at F10.
ASI2600MM Pro camera Bin 2x2.
30x60 sec exposures

I was only able to use 20 of the frames, as the comet passed in front of a bright star for the last 10 frames.

Here are the plate solving results from the full FOV from the middle image of the series.
******** ASTROMETRIC SOLUTION RESULTS ********
Center RA (2000.0): 15h 40m 50.88s
Center Dec (2000.0): -14° 59' 37.6"
Scale: 0.5510 arcseconds/pixel
Size (pixels): 3124 x 2088
Angular Size: 0° 28' 41" x 0° 19' 10"
Position Angle: 0° 29' from north through east
FWHM: 4.11 pixels, 2.26 arcseconds
***********************************************
The comet has now passed the Meridian and is heading into the light pollution dome of Brisbane.
 
Dennis.

   

   

[Dennis]

This is a full res 1600x1200 crop of the output from Tycho Tracker with the ASI2600MM Pro Binned 1x1.

Some thin cloud moved in towards the end of the series as the comet got lower into the light dome of Brisbane.

This gave an Image Scale of 0.2750 arcseconds/pixel and a Plate Solve gave a FWHM of 10.16 pixels, 2.79 arcseconds.

Dennis.

   

   

[PMSchu]

Thanks Dennis,

Those are some more excellent images. What does it look like when the comet occults the star?

I used to work with an optical engineer named Dan Grieser (the MP (10482) Dangrieser is named for him) who wanted to record an absorption spectrum of a comet as it occulted a bright star. Unfortunately we were never able to get a comet to cooperate. With today's equipment I think he would have been more successful.

Phil S.

[theskyhound]

Hello Dennis - how would you like me to attribute your images?

[Dennis]

Hello Dennis - how would you like me to attribute your images?

Hi Greg

Feel free to use whatever convention is most suitable and in keeping with general practices in the work that you do.

It can be something as simple as "a SkyTools 4 user, Dennis, in the Southern Hemisphere" or something along those lines.

Let me know if you would like any further technical details reagrding equipment used, etc.

Thanks.

Dennis.

---

Thanks Dennis,

Those are some more excellent images. What does it look like when the comet occults the star?

I used to work with an optical engineer named Dan Grieser (the MP (10482) Dangrieser is named for him) who wanted to record an absorption spectrum of a comet as it occulted a bright star. Unfortunately we were never able to get a comet to cooperate. With today's equipment I think he would have been more successful.

Phil S.

Thanks Phil, I'll dig out the frame(s) of the occultation and post any results.

Dennis.

[Dennis]

Thanks Dennis,

Those are some more excellent images. What does it look like when the comet occults the star?

I used to work with an optical engineer named Dan Grieser (the MP (10482) Dangrieser is named for him) who wanted to record an absorption spectrum of a comet as it occulted a bright star. Unfortunately we were never able to get a comet to cooperate. With today's equipment I think he would have been more successful.

Phil S.

Hi Phil
 
Thank you for sharing that story about your colleague Dan Grieser, I only wish he could have been in my back garden at the time with his spectrometer.
 
The comet occults the star on Frame 0027 in my 0001 to 0030 series.
 
For the star, SkyTools 4 writes:
 
J154050.7-145951
Single Star
R.A.  15h40m50.7s Dec. -14°59'51" (2000) in Libra
Magnitude: 15.72
Apparent Data for 2025 Aug 27  GMT+10 at Back Garden:
Apparent RA:  15h42m17.2s, Apparent Dec: -15°04'50"
Mean extincted magnitude: 16.3
 
I have included the following: 

• 1920x1200 crops of the comet aligned on the stars (Sidereal Rate) and aligned on the comet (Tracked).
  
• Tycho Tracker image file aligned on the stars, up sampled by x2 cropped 1600x1200 (Sidereal Rate) with the comet trailed.
  
• A screen copy of SkyTools 4 for the date/time of the transit.
  

 
Dennis.

1920x1200 crop Aligned on stars (Sidereal).
   

1920x1200 crop Aligned on comet (Tracked).
   

1600x1200 crop up sampled by x2  Aligned on stars (Sidereal).
   

Screen copy of SkyTools 4 showing the transit.
   

[PMSchu]

Dennis, that is so cool! 

Unfortunately at 15.7 magnitude I doubt that Dan would have been able to detect that star. Plus parallax would probably shift the position so there wouldn't be an occultation in Columbus. Still I'm glad that you were able to catch it. 

Thanks,

Phil S.