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#1 matti_94

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Posted 15 August 2014 - 09:47 AM

How can I calculate average brightness, number of the stars and age of m13? I have photo (luminance) from newton 8". I know that my calculate will be not to accurate from amatour telescope but i want to know the idea, way how to do this and the fact that it is possible.



#2 csrlice12

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Posted 15 August 2014 - 09:52 AM

I dont believe we've built a scope yet that will show you all the stars in M13....



#3 matti_94

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Posted 15 August 2014 - 10:20 AM

csrlice12, I know that but i want to know the method of this calculates, not great results for publication. Can you help me?



#4 Tony Flanders

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Posted 15 August 2014 - 12:08 PM

How can I calculate average brightness, number of the stars and age of m13? I have photo (luminance) from newton 8". I know that my calculate will be not to accurate from amatour telescope but i want to know the idea, way how to do this and the fact that it is possible.


I don't think you can calculate the number of stars in a globular cluster based on an image from an 8-inch scope -- simply not enough data. And without knowing the number of stars, you can't calculate the average brightness.

Average brightness isn't a terribly useful concept. Remember that the great majority of all stars you can see -- in a cluster, in the sky, anywhere -- are way above average brightness. It's a selection effect. The faint stars greatly outnumber the bright ones, but you can't see the faint stars.

There was an article in the December 2010 issue of Sky & Telescope about computing the H-R diagram of star clusters from amateur images. That would be the starting point for determining the cluster's age.
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#5 matti_94

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Posted 15 August 2014 - 12:51 PM

I can't find it. Give some link or maybe photo of article, please.



#6 csrlice12

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Posted 15 August 2014 - 01:34 PM

You can start here--http://en.m.wikipedi...Characteristics



#7 Tony Flanders

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Posted 15 August 2014 - 03:27 PM

I can't find it. Give some link or maybe photo of article, please.

It's available for sale at http://www.shopatsky...magazine-issues. Posting a copy of the article would be a copyright violation, sorry.



#8 csrlice12

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Posted 15 August 2014 - 10:09 PM

Believe this may answer your question, but its way over my head.Attached File  1992AJ____104_2104L.pdf   228.82KB   17 downloads



#9 ggalilei

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Posted 17 August 2014 - 08:01 AM

Nicely done, csrlice!



#10 matti_94

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Posted 17 August 2014 - 01:41 PM

Thanks. Next thing. I want to divide my photo for small rectangle (same size) or rings (with same area)  from the center of globular cluster and calculate ADU there. It's needed to make a histogram of distribution of star(luminosity on photo), then curve which is fitted to the histogram. I know that maxim can make a rectangle (and sketch curve), but i want to make many rectangles (same size) on the photos. Do you know program which can do this?



#11 csrlice12

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Posted 17 August 2014 - 04:44 PM

For that, you're well beyond me.  I'd think you'd be better off asking that in the AP forum....



#12 matti_94

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Posted 19 August 2014 - 08:22 AM

Thanks for links. I know already that in Maxim i can do it, graph window→horizontal box→export and you know ADU for every pixel in excel table.








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