[SkyViking (Rolf)]

Thanks for all your kind comments. I have added two more diagrams for M4 and M80 and changed the calculations slightly. First of all I now use the B and L files instead of B and R. This way the diagrams can be more easily compared to the standard B-V colour index used in astronomy.
I have also improved the Gosu program I mentioned, so it now takes the interstellar reddening into account. This is important in order to get the correct colour index rather than the observed one.
Hope that makes sense. I have updated the info on the site accordingly: http://www.pbase.com/rolfolsen/colourmagnitude_diagrams

Originally Posted by Mighty_oz

Lovely shot, nice presentation of a cluster

Thanks Marcus This one is quite photogenic right next to the bright star.

Originally Posted by RickS

Very cool, Rolf. Nice colour in the image too.

I hadn't heard of Gosu. The language comparison page lists not being Lisp as a language feature which is a little unfair. Once you get past all the parentheses some Lisp variants aren't that bad

Cheers,
Rick.

Thank you Rick, yeah Gosu is a fairly new language. Very 'clean' and not as verbose as Java but still with full access to all the solid Java API's. Very promising I think.

Originally Posted by alistairsam

Nice Analysis Rolf, is this commonly done?
would it indicate that there are a larger number of cooler stars?
what is your inference?

Thanks Alistair Yes these diagrams are standard astronomical tools but it's good fun to be able to create them from amateur data. There are quite a few interesting things visible in the diagrams, I'm thinking of making an annotated version.

Originally Posted by jsmoraes

Amazing idea. Congratulations for yours efforts. The graphics shows only magnitude or the actual color of stars too ?

Thank you Jorge, the horizontal axis is the colour index calculated as B magnitude minus L magnitude.

Originally Posted by multiweb

Very cool Rolf and a superb shot to boot. Great stuff!

Thanks very much Marc, glad you liked it

Originally Posted by Terry B

Very clever and well done. Nice examples of HR diagrams. It would be worth doing the same thing for an open cluster as well as they are a different age to GCs.

Thank you Terry Yes I'll try open clusters too, I just didn't have a good image of one where the stars are not overexposed (can't measure magnitudes correctly for saturated stars)

Originally Posted by allan gould

I read this and was just so impressed about what you have done. Absolutely brilliant and by the way, a great image.

Thank you very much Allan. It's a great little excercise, I'll probably add some more diagrams along the way.

Originally Posted by marco

Fantastic idea and extremely interesting result Rolf, I was not aware that such kind of analisys could be at the reach of amateurs.. I find the graphs really educative and interesting!

Clear skies
Marco

Thanks Marco Glad you liked it. I believe there are lots of things amateurs can do, we just haven't thought of it yet - too busy taking pretty pictures!

Originally Posted by Ross G

A great photo Rolf.

Nice contrast and composition.

Ross.

Thank you Ross, it's a pretty target I think.