I went to bed believing that this object was too faint for my system, with PixInsight crashing as I tried to process the frames.
This was on top the The Sky X freezing when frames were being downloaded from the ASI 2600 MM Duo using the X2 Plug In and the native ZWO Drivers, all freshly installed from the ZWO website.
This morning, I tried again using CCDSoft to Calibrate, Register and Stack the 30x60 sec exposures, with the Stack Mode set to Maximum and Voilà – there she was.
Tak Mewlon 210 F11.5
Tak x0.8 Reducer/Flattener
ASI 2600 MM Duo
A Plate Solve calculated the imaging system to be F/10 at 2100mm.
Pixel scale: 0.742 arcsec/pixel
Thanks Steve – I also managed to figure out why PixInsight was crashing – user error!
In the File List, I noticed a couple of files that had an additional “process” letter in the filename and when I removed them, PI worked just fine. I guess that is why we should not be processing at 2:00am!
I managed to combine 2 sets of images (straddling 10:30pm and Midnight) that show the trail of C/2025 N1, as shown in the red circles.
It is a bit ugly, due to compression to get the file size below 200KB.
It is nice seeing your early images of the interstellar traveller.
Thanks Pierre, this object is so faint!
Last night, I downloaded an Ephemeris from the JPL Horizons website for 3I/ATLAS for 2025-07-04 as observed from our back garden and used the data to generate a TSX Pro Database (SDB) which plotted the position of 3I/ATLAS every 5 mins over that period.
This is a stack of 24 frames taken on 2025-07-04, from 9:06PM to 9:54PM (AEST).
2025-07-04 11:06:00 UT to 2025-07-04 11:54:00 UT.
Tak Mewlon 210 F11.5 with Tak x0.8 Reducer/Flattener.
F10 at 2100mm focal length.
ZWO ASI 2600 MM Duo camera
24x60 sec exposures.
I set the Stack Mode to “Maximum” (Default=Average) as the object was very faint and I wanted all the data to “poke” through the BG.
I find it amazing that we (you) have the technology to do these sorts of things, whereas our ansestors could only gaze in wonder with their own eyes.
You are so right Pierre.
It is breathtaking how the various hardware and software components have developed over the last 10-20 years, literally at an astronomical rate.
I think that today, we are living in a golden age of astronomy.
The variety and technical sophistication of the mounts, OTA’s, applications, cameras, accessories, on-line data resources, how-to videos and imaging techniques available to the amateur today is mind boggling.
Here are some rough observation planning notes I have put together for Interstellar Object 3I/ATLAS.
I have used position data currently available from Stellarium, lunar ephemeris data from Sky Tonight and magnitude data from the Minor Planet Centre. The calculations are for Melbourne at 8pm Australian Eastern Standard Time (AEST) but can be extrapolated for observing around Australia.
The predicted best viewing / imaging nights for the next few months are:
No moon, 14 July to 26 July. Altitude 55 – 67 deg. Constellation Ophiuchus.
No moon, 12 Aug to 24 Aug. Altitude 64 – 51 deg. Constellation Scorpius/Libra.
No moon, 10 Sept to 22 Sep. Altitude 29 – 14 deg. Constellation Libra.
The object is expected to brighten throughout this period as it moves closer to the Sun.
Visual observers may need large telescopes (12 inches of aperture or more) in very dark sky locations under excellent conditions to have a chance of seeing the object during these earlier dates.
Astrophotographers will be able to image this object on a wider range of nights, depending on their equipment and skill.
After September, the object will not be visible from this location. It will be visible again from around 1 December, just above the Eastern horizon in the early morning.
Last edited by Pierre_C; 11-07-2025 at 06:44 PM.
Reason: Updated ephemeris data
Interesting capers Pierre,
Seen a news report last night and here this has been subject for a week, good stuff and be a lot of astronomical data collected from all sorts, even the big guns & prob including James Web to try and hunt out substance signals considering it is assumed to have come from another star-system, not proven though. fascinating none-the-less,,,,
Grouse images Dennis,,
You definitely have the skills to catch this interstellar traveller, speshly being this early in the piece and the fact it's a fraction the size of 'Oumuamua.
Be spectacular if it out-gases on closer approach.. Nice work..
It provides a link to Gideon van Buitenen’s website which provides an interactive orbit chart, a light curve and position chart. https://astro.vanbuitenen.nl/comet/3I
The two scientific papers referenced in the article have contributions from individuals at Curtin University and University of Melbourne:
I have updated my observation planning notes (post #12) with freshly downloaded data from my desktop version of Stellarium. The data I originally used from the Stellarium mobile app on my phone gave a different path.
Can anyone comment on the accuracy of desktop Stellarium comet data? Is it accurate enough for confident identification of an object such as this?
Not sure about Stellarium, but I understand that the eccentricity of the orbit of C/2025 N1 precludes it from being displayed in The Sky X Pro as an object you can track. It lies above the upper limit of typical comets than can have their elements imported into The Sky X Pro.
However, by downloading an Ephemeris from JPL Horizons you can create a Sky X Pro Database which then displays the position of the comet (every say 5 mins if that is the time interval you choose) and then the mount can slew to the comet.
Here is last night’s effort as displayed in Tycho-Tracker, showing the sprinkling of a trail and then tracked and centred on C/2025 N1 (ATLAS).
I took 2 sets of 30 exposures at 60 secs per frame.
Taken with C11 Edge HD at F10 (2800mm) and ASI 2600 mm Pro (not Mewlon 210 as in info panel). The seeing was quite poor with the jet stream quite active overhead.
Thanks for your thoughts on the ephemerides, Bojan and Dennis.
I am doing some planning for when the object is bright enough to see through my 8-inch refractor telescope and for my basic 4-inch refractor and DSLR imaging setup to capture.
I compared the Jet Propulsion Laboratory (JPL) and Minor Planet Center (MPC) data to the position data in Stellarium, and while the JPL and MPC data were almost the same, there was a small difference of around 1-2 arcminutes in Stellarium. (I am not sure why there was a difference).
In comparison, the field of view in my visual setup is around 24 arcminutes (at x150 magnification) and around 1.3 x 2.0 degrees in my imaging setup. So, I think that if I point my telescope in the general direction using stellarium, then it will be very likely that the object will be in the view.
Given the current apparent angular velocity of 1.4 arcseconds per minute (and increasing) according to JPL, it seems to me that if the object is bright enough to see, then when I observe over one hour I should see an apparent movement of 1.4 arcminutes, which should be noticeable against the background stars.
Similarly, if my imaging setup is able to capture enough light from the object to show up above background noise, then collecting multiple images over a one-hour real time window should give me a trail of approximately 1.4 arcminutes, which hopefully will be discernible in the frame. (Dennis, I think this is consistent with the approximate 0.7 arcminute trails in your latest sets of 30 exposures at 60 seconds per frame?)
So, my overall approach will be to use Stellarium to find the general direction of the object; observe for one hour looking for movement; image for one hour looking for a small trail; and confirm what I see using the JPL position data.
