Forum der Vereinigung der Sternfreunde

On 2024 November 19 at about 2330UT 37P/Forbes and C/2023 C2 (ATLAS) had a conjunction as observed from Earth. This animation is from 2024 November 20 0137-0234UT after the conjunction when the 2 comets moved from 1.7' to 2.5' from each other. 37P is the brighter of the 2 comets around magnitude 14 and C/2023 C2 is about magnitude 16 in this animation, need to run calculations in Astrometrica later for the new telescope and camera setup to accurately determine the comet magnitudes. Unfortunately, thin clouds moved over the area during the collection of the images and the comets were only 8 degrees above the horizon for the last image in the animation, so the animation is rather rough to look at.

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Cheers, Mike
Arizona

I swa it already on the meailing list. Great observation! Unfortunately, far too dim for us visual observers.

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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

Astrometrica software used several hundred stars in the FOV to determine that my old eyes using only a few stars did not do a very good job of estimating the comets magnitude in the animation above. On 2024 November 20 UT 37P/Forbes was magnitude G=12.5 and C/2023 C2 (ATLAS) was magnitude G=14.1 as calculated from 18x10 second images in an aperture diameter of 1' and 0.7' respectively. The comets were 2.1' apart at 0202UT when these calculations were made. Yes, I forgot to flip the animation images horizontally to take into account the camera sits at the front lens of the RASA telescope.

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Cheers, Mike
Arizona

dear mike,
nice observation, wish i had your Arizona weather conditions and not the german november fog ..... And good luck with your new RASA 8 !

Roland, thank you. What surprised me was how bright 37P is right now, I was expecting both comets to be about magnitude 14 when I went to do the simulation, so I was a little confused when that first image was taken and there was a much brighter comet on the screen that what I was expecting. On November 1, I observed 37P around magnitude 14.5 which a little fainter than what Seiichi's magnitude curve predicted and ATLAS in Chile had it at magnitude 13.8 on October 31. What is interesting is that at about the same time Thomas using a remote site reported 37P was about magnitude 12.3. All of the reported observations on Seiichi's site had the comet at about magnitude 14 or fainter until Thomas reported it at magnitude 12.3 and from my images on 2024 11 20 it is still at about magnitude 12.5. Not making excuses, but the only conclusion that I can come to is that when I took those images on 2024 11 01.1 37P had a very bright part of the Milky Way Galaxy behind it in part of the image and I was using only a 50mm refractor so maybe that led to Astrometrica calculating a much different magnitude than what Thomas observed at 2024 10 31.8. The other difference is that I used an aperture diameter of 1' and Thomas used an aperture diameter of 3.3' which would result in my observation being fainter, especially with the Milky Way Galaxy glare behind the comet. All of this just goes to show that no matter how hard we all try to get accurate magnitude measurements there are still a lot of parameters that can make a big difference in the results. Thank you, Thomas, for letting me use your data that you observed for 37P and I welcome your thoughts on what I have just said. The bottom line is that 37P evidently had a brightening event at some point in the last month that I was not aware off, I used an aperture diameter of 1' again on my latest image to determine the comet's magnitude. Roland, I would love to have that big 16" telescope of yours sitting in my back yard, I have the RASA8 so that I can move it around some to try and avoid all the houses, lights, trees and cactus in my neighborhood to try and observe all those nice comets that always seem to be near the horizon when at their best. You have to suffer the clouds in the winter months, in Arizona it is cloudy almost all of the summer which I never would have expected when I moved to the desert. Denver was the best area I ever lived in for clear skies most of the year.

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Cheers, Mike
Arizona

37P on the evening of 2024 December 4 0147UT was magnitude G=12.9 as calculated from 21x10 second images taken thru a green filter in an aperture diameter of 0.8'. The comet continues to be about a magnitude brighter than predicted.

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Cheers, Mike
Arizona