Spectroscopy is essentially analysing the light from an object and seeing how the intensity of the light varies as a function of wavelength (i.e. looking at the spectrum of the object). This can reveal all manner of things such as the temperature of the object, what it is made of and how fast it is moving. This is detailed analysis that needs finely tuned equipment and the Star Analyser tries to fill a gap in the low end of the market - it won't show the detail but it's fun, easy to use and informative.
The Star Analyser is just like a standard filter - it screws into any eyepiece and off you go. When combined with my webcam it means I can take pictures of stellar spectra for further analysis. Here are some spectra I took of Arcturus:
As you can see, the results are very consistent and show some detail - the red appearance of Arcturus is obvious and the dark line on the middle-right is one of the Fraunhofer absorption lines due to oxygen in the Earth's atmosphere.
To show the difference between a relatively cool K-type star like Arcturus and something a bit hotter, here's a spectrum taken of Sirius an A-type star:
The spectrum is much more green/blue and other features are visible such as the H-Beta line in the light-blue section.
Another interesting use of the Star Analyser is to compare stellar magnitude. I find it much easier to compare the brightness of two spectra rather than looking directly at the stars. Providing I keep the webcam settings the same and compare stars of the same spectral type then I get a decent comparison of magnitude. I tried this with the main stars in the Plough (which are mostly A-type stars) and got a magnitude comparison and therefore distance approximation. I haven't had much chance to play around with this yet and feel it needs a new post anyway! I'll also follow this post with a description of how to get a spectrum from using the Star Analyser.
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