Forum der Vereinigung der Sternfreunde

Did not expect to see 48P/Johnson with an elliptical coma 1' long by 0.5' wide with a 2' long tail at PA248 degrees from images collected on 2025 July 26. 2 different magnitude calculations gave G=15.8/15.7 in an aperture diameter of 0.6'. Would be interested if someone could provide some history on 48P that may explain what we are observing, Michael and other's images are showing the same comet features.

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Cheers, Mike
Arizona

mike, nice images, the comet is already fading, the attached image is from this morning, 18.08. with the 16", no explanation for the odd appearance ....

Thomas was kind enough to post a reply on Maik's "Comet-ml" page explaining the appearance of 48P in our images the past few months. Thomas referenced a tail simulation of 48P as it has crossed the ecliptic plane created from Uwe's simulation program. It would be nice if Thomas or Uwe would reply to this message with that simulation and explain what it is showing us about 48P's tails and current appearance. From the simulation it appears that we should observe the comet over the next few months to follow the tails and see how they compare to Uwe's simulation, should be interesting. I had looked at Gideon van Buitenen's Solar System simulation of 48P which showed that 48P had recently crossed the ecliptic plane and was below the plane when my images were collected, but without the simulation for an explanation could not be sure that was the answer to what I was observing. Thank you, Thomas and Uwe, for explaining to me what my images were showing.

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Cheers, Mike
Arizona

Dear Mike, my simulation software calculates the places of single particles. These particles follow different orbits each because of ste radiation pressure. Assuming an emissina rate and an emission spectrum the program calculates how a tail is formed in the orbital plane of the comet (2D). This is projected to the geocentric view afterwards.
Everybody may have this software, it is Java. At one of the meetings of the German group, I gave a lecture how to use it. It is a command line application with tons of parameters... But it has a graphical output.

Some years ago I hold an English lecture about this, the slides still exist. Probably you may learn something from them.

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Uwe Pilz, Fachgruppen Kometen und Astrophysik/Algorithmen.
Oft benutzte Instrumente: Fujinon 16x70 FMT-SX-2, TMB Apo 105/650, Skywatcher Evostar 120/900 ED, Ninja Dobson 320/1440, Smartscope Dwarf-3