I wanted to try something "different" this time since the nights are so short. I captured 20 different bright stars with 60x10s frames with my OSC. Revision A shows all images merged into a collage. Looks kinda cool already but that's not the goal... the goal is to play around with the star colors .
So I collected the star colors of each star's halo with the color sampler tool (11 by 11 pixel average). Then I converted those colors into HSV colorspace:

As a next step, I converted those colors into a wavelength representation:

Therefore, I just use the "hue" and neglected the "saturation" and "brightness" value which is the first inaccuracy. In accordance with the Asi071's & UV/IR cut filter's sensitivity, I should be able to acquire light from 400nm - 680nm, which also narrows down the effectiveness of this approach.

Revision C-a shows a summary of those calculated wavelength for all 20 stars. Revision C-b and C-c shows the color index and temperature values (for further explanation see below). Note that wavelength, color index and temperature show the same course (which is already pretty cool ).


After "calculating" the wavelength, I implemented Plank's law and reverse engineered the black body temperature for the assumed peak wavelength:


Revision D shows the black body curves for some of those stars:

Note that Revision D shows examples based on the GroundTruth temperature (based on catalogue values). The temperatures that I actually calculated are given in Revision C-c. One can clearly see that the used method is too inaccurate to deliver the real star temperatures. But (especially for the colder stars) it already provides good approximation values .

A fun thing to do with those temperatures however is given in Revision E. Together with the absolute magnitude (derived from catalogues), we can build up a Hertzsprung-Russel diagram.



In the beginning I was pretty disappointed. Because I was hoping to get a diagonal distribution like the main sequence stars... something like this:



But when I overlayed both plots I realized it


All the big red stars that I chose: Pherkad Minor, 6 Draconis, 28 Leonis Minoris, Althiba IV, Althiba V, Althiba VI, Kochab, Tania Australis, 2 Herculis and HIP 50951... they are coincidentally ALL classified as "Giant stars" . And therefore the representation is correct

Summary: I had a lot of fun with this project and I learned a bunch of things over star colors. I didn't give much of explaining to the plots, sorry... but I am planning to do some additional projects like this and I'll insert structured background information there (I already found some cool examples of spectroscopy that I wanna try out).
Also a fun story: During my research I hurt my brain over a simple question With respect to Stefan-Boltzmann-law... why starts a hot iron to glow red > orange > yellow > white (and would continue to glow blue etc.) ... without glowing green? Green is the middle of the spectrum after all... why doesn't it glow green? Why don't stars shine green? It took me an hour to find the answer (turns out to be nothing that's easy to google) and it's soo logic maybe I made you curious.