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Classic Rich Field

classic dso equipment eyepieces LP observing observing report refractor sketching
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#676 Organic Astrochemist

Organic Astrochemist


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Posted 13 August 2022 - 04:10 PM

As an example, I was intrigued this year by the differences I was able to observe between M10 and M12 when I really concentrated on comparing them. This under dark skies with the 114 mm Starblast f/4 at 112X or 188X.
As your data and that of others show the two clusters have similar apparent and absolute magnitudes (M10 is slightly brighter), very similar distances, and M10 has only a slightly larger radius. However, I had the distinct impression of resolving many more stars in M10 (a larger instrument or camera would have resolved more in both). This observation seems consistent with the data that suggests that M10 is twice as massive as M12 and therefore has many more stars on the RGB spread out over a slightly larger area that allowed me to see them fleetingly.


It’s unfortunate that your observations of these two clusters were done with very different equipment. Perhaps you will revisit them some day.

Edited by Organic Astrochemist, 13 August 2022 - 04:13 PM.

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#677 AllanDystrup



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Posted 15 August 2022 - 01:44 AM


WOW OA, -- Talking about learning a lot!


     I thank you for a very interesting analysis and perspective on the GC classification system!


     Personally (and like you), I've never been a fan of the SS concentration-class classification of the GCs, being purely morphological as seen from our local perspective of the solar system; In that way it is like the "Gould's Belt" description of the OB-associations: it is lacking crucial parameters of object mass, chemical composition and 4D kinematics, and thus missing out on the most interesting aspect of origin and evolution of these objects.


     Luckily today, with the ESO GAIA data, we DO have approximations for these parameters, and thus a much better foundation for building our understanding of the astrophysics of Globular Clusters.


     Also, thank you for the link to the website with "Fundamental parameters of Galactic globular clusters" (by Baumgardt et. al.) -- a comprehensive, very useful aggregation of up-to date GC-data, including kinematics, CMD, mass and rotation graphs. I'll be using that a lot as a central reference in the future! As you suggest, this updated knowledge of mass and CMD-data (RGB members) will allow a more well founded interpretation of what we can observe here from earth with our humble amateur equipment.


Thanks again OA, always a pleasure and inspiration reading your analysis and comments on these projects!
     -- Allan

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