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Here is an animation of its final hours taken from LASCO C2:
https://britastro.org/observations/observation.php?id=20260405_091544_fe658e5ddc7bfd61
Yes, it broke up prior to perihelion and nothing came out at the expected position so there will be no headless wonder in the evening sky. That’s a shame but it was always a significant possibility given the small size of the nucleus.
Some of the dust released ahead of the breakup did appear to survive, and is visible in the coronagraph images, as a dust cloud on the “wrong” side of the Sun. This could possibly be detectable as a very low surface brightness feature in the morning sky. Highly unlikely, particularly since the Moon will interfere, but imagers are a resourceful bunch.
We’ll see.
It is currently behind the occulter in C2 but we should get an indication about whether it has survived in few hours.
https://soho.nascom.nasa.gov/data/realtime/c2/
You can make a movie using this page:
That really is a beautiful image. The full-sized image is here:
https://images-assets.nasa.gov/image/art002e000192/art002e000192~orig.jpg
the EXIF suggests that this was taken using a Nikon D5, 22mm, f/4, 1/4s, ISO 51200. Apollo 8 had the famous Earthrise photo. I think this is better.
That’s a shame, but it was going to be a difficult observation anyway. Still worth keeping an eye on the launch time and ephemeris for interesting opportunities from the UK.
If the launch takes place as currently planned (April 1, 22:24 UTC) we may be able to see the Trans-Lunar Injection Burn from the UK 25 hours 37 minutes later so around 2026-04-03 00:01 UTC although the spacecraft will be low above the SW horizon. An ephemeris is available from JPL Horizons.
From Chelmsford the spacecraft rises around 23:49 on April 2 and at the time of TLI it will be 10 deg up at an azimuth of 209 deg.
Almost 60 years ago, on 1968 December 21, Chris Taylor saw the Apollo 8 TLI from Chelmsford. There is a really good S&T write-up here:
https://skyandtelescope.org/stargazing-and-observing/stargazers-corner/apollo-8-view/
I would like to reproduce that observation!
A lot of the topics covered in this thread are dealt with in detail in the 2017 review paper I cited in my original news article on this comet:
https://link.springer.com/content/pdf/10.1007/s11214-017-0446-5.pdf
It is well worth a read. See, for example, section 6.2 which discusses the breakdown of the inverse square law in relation to, amongst other things, heat flux.
Peter – Nice image from Spain. I actually managed to get it from Chelmsford a couple of nights’ ago but the image is very grotty.
Paul – Yeek. You’re right! very embarrassing but spelling was never my strength! I do feel a right Fule.
Since we are getting picky here I need to point out the difference between power (measured in Watts) and energy (measured in Jules). 1W = 1 J/s. The power flux density (in W/m^2) is not the same as the energy absorbed (which will be in Jules).
The PFD at distance r is easy. It is simply the Sun’s total radiant flux (P=3.8E26 W) spread over an area which is the surface of a sphere of radius r so:
PFD = P / (4 pi r^2) [W/m^2]
If you put in 1 au (r = 1.5E11 m) you get a PFD of around 1.35 kW/m^2 which is our nice, familiar solar constant. If you put in the comet’s perihelion distance (8.55E8 m) you get the aforementioned 41 MW/m^2. That is indeed a lot!
As Paul points out the energy absorbed is much more complicated since it depends on the albedo. It also depends on how long you integrate over. Also, the comet’s nucleus will get very hot and so it will be radiating energy the other way. Depending on the thermal conductivity of the surface layer it might get close to thermal equilibrium with the photosphere. That is an exercise for the reader.
Whatever happens, it isn’t going to be nice. Add to that the tidal forces being that close to the Sun (they go as 1/r^3) and it is a big question whether it will survive. That will depend on how big and consolidated it is. We get a ringside seat since we’ll be able to see it as it passes through the field of view of space based coronagraphs.
What other Solar System objects do anything as exciting as this?
That’s a great Christmas story. Lick is a wonderful place. In fact it is one of my two favourite observatories in the world. The other is Lowell. Both are observatories built on a human scale and both have wonderful Clark refractors. Both also have great staff who make visitors feel very welcome.
The latest source code is here:
https://nickdjames.com/astrolinux/20260223.tgz
You’re welcome to have a go at building it but it does have a lot of dependencies so that might be a challenge. First build the libraries using “make -f Makelib” and then the tools with “make”.
Bear in mind that this is code I have written for my own use so bits of it may not work or may only partially work for specific situations. It is also completely unsupported and you use it at your own risk.
You might find Magic Lantern (https://www.magiclantern.fm/) useful. It allows you to script things in the camera.
This is for orbital data centres and the business case seems pretty tenuous compared to comms systems like Starlink. The actual FCC application is here:
although you need to register to be able to download the details. As far as I can see this would be launching solar powered data centres to support AI so hopefully that bubble will burst well before this gets anywhere. The proposal would be to put most of the satellites in high (up to 2000 km) Sun Synchronous Orbits (SSOs) so that they remain illuminated most of the time. That would be a nightmare for astronomy within a few thousand km of the terminator where these things would be visible well beyond astro twilight.
Indeed a terrible loss. Allan was an amazing and knowledgeable character but was also very down to earth and great fun to be with. To see him and Patrick together and in full flow was a sight to behold. The book Denis mentions, “The Victorian Amateur Astronomer” is a fascinating read and could only have been written by Allan.
To be clear EQMOD is a Windows app under ASCOM although I think it might run under Linux with INDI. It is open source and has been around a long time so it is very stable. It uses a pseudo-serial interface either directly via USB for recent mounts or via a USB to serial cable for older mounts.
It is very difficult to interpret these images!
Part of the problem is that the original FITS image standard was not clear on the row order. Professional tools tend to assume that the origin is in the bottom left corner so rows are numbered upwards from the bottom. Many amateur tools assume that the origin is in the top left corner so that rows are numbered downwards from the top. If you open the file with a tool which assumes the opposite convention you get a mirror image. There is now a FITS keyword (ROWORDER) which signifies the order to use but many tools don’t recognise that. I would think that the HST FITS files have their origin at the bottom left. I haven’t used PI or Astroart and I don’t know which convention they follow.
At present the prominent tail of 3I is in a PA of 100 degrees, i.e. just south of east. You can see some recent images here:
https://britastro.org/cometobs/3i/thumbnails.html
Could you post the greyscale stack that you get prior to doing the LS filter please along with some scale information? We could then compare with other images to get some idea of the orientation. Also, let me know the parameters you have used for the LS filter. You need to be very careful with that since it can easily generate radial structures that are not real. As a rule of thumb you should keep the rotation to 15 degrees or less.
If you use ASCOM/EQMOD the custom rates can be set for both axes in the “track rate” box. See attached pic.
Attachments:
This is a hangover from the old days when mounts didn’t have motors on the dec axis and all you could do to track the sun and the moon was to change the RA axis drive rate to match their average eastward drift rate. Most mounts now have the ability to move in both axes and if you control them via software using, say, ASCOM or INDI, you should find that you can program offset rates based on the true ephemeris or, at least, some calculated offset rate. As Dominic says, there is usually some backlash in the gear system so that reversing direction is problematic but that is only really important for guiding, not in this case where any significant tracking offset is always in one direction.
It sounds as if something is very broken in that C14 if you can’t move the focus to within 30cm of the back plate. Ron was good at taking things apart and generally good at putting them back together again. Maybe he got something wrong with this one.
That seems very wrong. I have used a low-profile focusser on my 11-inch conventional SCT with the camera sensor only around 80mm from the rear of the scope. In fact, I’ve used planetary cameras directly on the back of them without an external focusser, probably less than 40mm from the back.
Maybe the 14-inch is different but I doubt it. Where did this one come from?
