Forum der Vereinigung der Sternfreunde

Liebe Kometenfreunde,

Klaus Wenzel aus Großostheim hat die Begegnung von 62P und 29P fotografiert. Ich hatte darauf in S&W hingewiesen. Die Aktivität von Schwassmann-Wachmann lässt sich ja kaum vorhersagen, und so ist er auch recht matt. Klaus schrieb:

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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

Prima. Die Begegnung hätte ich auch gern festgehalten. Allein das Wetter hat nicht mitgespielt.

Hallo Forum,

ahh, hatte doch jemand Glück.
Schöne Aufnahme. Ich hatte leider Bewölkung.

Gruß
Christian

Der Komet entwickelt sich prächtig. Ich hatte heute morgen eine zutreffende Wettervorhersage und es klarte 4:40 auf. 62P war groß und hell im 6" Refraktor. Gut kondensiert. Eine Größenklasse heller sollte er noch werden bis Ende des Jahres.

Maik

Hier ist als Nachtrag noch meine Remote-Aufnahme der Begegnung beider Kometen. In der Tat ist das eher ein Zufallsprodukt, denn ich hatte nur 62P im Visier und nicht mehr an die enge Begegnung gedacht. So steht 29P unverhofft mit im Feld, etwas an den Rand gerückt.

Die Bedingungen zur Zeit der Aufnahme waren nicht so gut, hohe Bewölkung mit 0.5mag Extinktion haben helleren Sternen einen riesigen Hof beschert. Der Sternhaufen Praesepe steht rechts unterhalb des gezeigten Ausschnitts und ist alles andere als schön anzusehen. Trotzdem möchte ich einen Bildausschnitt zeigen, denn hier sieht man mal recht eindrucksvoll einen Kometen mit purer Staubkoma (bzw. kurzem breiten Staubschweif) - 29P links im Bild - und daneben einen Kometen mit purer Gaskoma - 62P in der Mitte. Der Staub "leuchtet" gelblich/orange während die Gaskoma kräftig grün erscheint.

Wenn man den Kontrast der Aufnahme extrem erhöht, sieht man wie riesig groß beide Kometen sind und bei 62P zeigt sich ein dünner (Gas-?)Schweif von ~15' Länge in PA=286°. Die Bestimmung der Gesamthelligkeit mit AIRTOOLS ergab:
62P - 2023 11 15.53 UT, m1=9.6, d=17'
29P - 2023 11 15.53 UT, m1=12.2, d=8

62P/Tsuchinshan under a moonlit sky on 2023 November 23 was magnitude G=9.1 at 0752UT as calculated from 10x30 second green filter images.

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Cheers, Mike
Arizona

62P/Tsuchinshan on 2023 December 6. Calculations on 15x20 second green filter images showed the comet was magnitude G=9.0 in an aperture diameter of 8'.

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Cheers, Mike
Arizona

62P on 2023 December 18 was magnitude G=7.8 as calculated from 12x20 second green filter images with an aperture diameter of 8'.

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Cheers, Mike
Arizona

Hello Mike, thank you for sharing your images on 62P. Unfortunately, your last brigthness measurement is heavily affected by two bright stars (G mag of 9.0 and 9.1) locating within the aperture. I'd also like to point out that the coma appears considerably larger in longer exposures making it even more difficult to determine its total magnitude from within Astrometrica. The amount of light from the comet within an 8' aperture is about 60% of the light I am measuring within an aperture of 25' diameter.
Cheers, Thomas

In der Nacht vom 17. zum 18. Dezember war es nach einer Pause von 2 Monaten hier endlich mal wieder halbwegs klar. Hier ist mein Ergebnis, einmal in Farbe und mit gleichem Ausschnitt als invertiertes Graubild. In letzterem erkennt man die Ausdehnung des schwachen Schweifs von etwa 2 Grad Länge besser. Belichtet wurde insgesamt 26 Minuten mit RASA 11" und ASI6200MC Farbkamera aus der Stadt Weimar heraus.
Vielleicht wird der Schweif in den kommenden Tagen noch etwas kräftiger. In dunkler Umgebung lohnt sich sicher auch eine tiefe Weitwinkelaufnahme ...

CS
Thomas

Hello Thomas. I freely show my data collected so that others like you can be as judgmental as you want to be. Rather than tell me what is wrong with my calculations why don't you show us yours and give your calculated magnitude from your large aperture which I am sure contains stars within your aperture used for the calculations. As far as what Astrometrica does to determine the comets magnitude, do you know for sure that those stars are not considered in the final magnitude calculation and corrected for them? Surprising that my calculations are now reflecting what is being reported in COBS since I am doing nothing right in your opinion. Everything about predicting a comets correct magnitude is judgmental in the amateur astronomical community, left up to the person collecting the data and what he assumes is the correct way to do it in his opinion. There is no standard, all one has to do is look at COBS to see that. You assume the comet diameter is what you see in your images, I suspect it is a lot larger but the outside fluff contributes almost nothing to the final magnitude calculations. Using a very large aperture to try to include every bit of the comets coma in my opinion results in very bogus results because of all the other variables which are not taken into account in that large aperture diameter which results in magnitudes for a comet being much brighter than they actually are. To simply sum things up, there is no standard for calculating a comets magnitude, everyone is doing his own thing based on what he or she thinks is right, camera calculations versus binocular calculations, what aperture diameter to use, green filter or no filter, different software and so many other variables. There is not much scientific about the way current comet magnitudes are calculated by amateur astronomers, everyone has his opinion and some think they know everything when with all due respect they know nothing more than the rest of us.

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Cheers, Mike
Arizona

Hello Mike, every brightness measurement of a comet within an indicated size of the aperture used is of value, as are yours! I didn't mean to criticize your work in any way. I fully agree with you that there is no standard in CCD/DSLR photometry and observed coma sizes are always dependant on instrumental setups, observing conditions and reduction methods. In fact the coma extends as far as the most distant dust grain/particle traveled away from the nucleus - there is no definition of THE coma size.

I do not know about internals of Astrometrica, so apologies if my assumption is wrong that your measurements are the result of a "simple" aperture photometry. On the other hand the increase of comet brightness between your last two reported measurements (1.2 mag) is quite a bit larger than what has been reported on COBS (on average 0.4 mag) and COULD be the result of the additional flux contribution of the two stars mentioned.

If you are interested in my brightness estimates submitted to COBS, please search for ICQ observer key "LEH02". My last measurements obtained from analyzing the green channel of the image I have posted is: 2023-12-18.00 UT, m=8.4 mag, coma diameter=24'
or when measured in an aperture comparable to your reports: m=8.9 mag within 8' aperture size.

Instead of GAIA G magnitude I am using GAIA GB and GR magnitudes and apply a color correction term during the photometric calibration (derived from 200-400 calibration stars in the field) but this makes not a big difference. I do however subtract all stars from the image before measuring any fluxes.

To sum things up: photometry of large diffuse comets has to be read with some care and the best we can do is continuous observation and sharing of our results and experiences. So, please continue your good work and lets hope for beautiful comets the next year ...

CS
Thomas

62P on 2023 December 31 was magnitude G=8.2 as calculated from 15x20 second green filter images with an aperture diameter of 11'. 83% Moon 20 degrees to the west.

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Cheers, Mike
Arizona

62P on 2024 January 3 was magnitude G=8.3 as calculated from 25x20 second green filter images with an aperture diameter of 11'. Red filter images showed a tail at least 7' long at PA 290 degrees.

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Cheers, Mike
Arizona

Endlich mal eine Schönwetterkatastrophe! Ich geniesse das Beobachten morgens und abends!

Heute morgen habe ich nach der visuellen Schätzung mal mit stehender Kamera 15 x 3 Sekunden den Kometen abgelichtet. Ergebnis anbei. Nichts Gewaltiges, aber schön, was mit relativ einfachen Mitteln möglich ist.

Maik

62P on 2024 January 9 was magnitude G=8.0 as calculated from 25x30 second green filter images with an aperture diameter of 10'. Maik, I have read with interest your comments about reporting information about comets on COBs. Gideon talked about the aperture radius reporting and suggested it should be reported as the aperture diameter. I agree with most of the comments on that topic and it does bring out the problem with reporting comet magnitudes, "there are no ground rules", thus so much variance in the reporting of a comets magnitude, if you don't understand the importance of reporting the aperture diameter (or comet coma width) you are using then you really don't know what you are reporting or reading, just to point out one of the many discrepancies in reporting comet magnitudes on many sites. I am not knowledgeable like most others on how this should all be reported, but it is time for the amateur community to agree to a common set of ground rules for both camera and visual reporting so that a true magnitude can be calculated from all the reports for each comet at any given time. When I present a comet magnitude calculated by Astrometrica the aperture diameter is given, this diameter is just a little larger than what I perceive to be the width of the comet coma from the images that I have collected. I provide images of the comet so that others can understand what I am looking at to come to this conclusion and I also have mono images that I may not present to help determine the width of the comet coma. But, this then leads to more questions, one astronomers coma width differs from what another astronomer sees on his images, so what is the actual coma width? I have come to the conclusion that what I see in my images is what I use for the magnitude calculation, and I make sure the aperture diameter completely covers that coma width, I am sure that I am not seeing it all, but it gets so faint outside of what I see in my images that there is not much to be added to the magnitude calculation. A magnitude G= comes from the latest Gaia catalog and a magnitude V= comes from the latest UCAC catalog. There are so many other variables that those who think they can reliably calculate a comets magnitude down to a few tenths are just kidding themselves. I enjoy your image of the comet, as you have stated, brighter comets can be photographed with minimal equipment and effort. I am sure that a lot of people who don't know much about astronomy or don't have much equipment would like to try to take an image like you did, they just need to know how you did it and what equipment you used.

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Cheers, Mike
Arizona

Hallo zusammen,

Komet 62P bewegt sich gerade durch ein Feld mit sehr vielen Hintergrundgalaxien. Gestern morgens habe ich ihn mit meinem 20" Dobson beobachtet. Aufgrund seiner recht großen Ausdehnung wirkte er am besten bei relativ geringen Vergrößerungen (74-128x). Der Lumicon Comet Filter half, den Kontrast der Koma zu erhöhen. Neben dem Kometen sah ich die Galaxie IC 3107.
Anbei meine Skizze.

Clear skies

Robin

62P/Tsuchinshan on 2024 February 5 was magnitude G=8.9 as calculated from 20x20 second images thru a green filter in an aperture diameter of 9'.

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Cheers, Mike
Arizona

The Full Moon was only 34 degrees to the west of 62P/Tsuchinshan on 2024 February 24 when these images were taken. 15x30 second images taken thru a green filter calculated the comets magnitude as G=10.0 in an aperture diameter of 6'.

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Cheers, Mike
Arizona