Using a Star Analyser - Blog

You're welcome Mike.
The purpose of this blog is to share what I am learning and hopefully encourage others to join in.
If anyone has any questions, of course, please ask.
Michael.

I mentioned earlier about the use of a Type A star to begin with.
Vega and Sirius are examples of Type A stars.
You may ask what are Type A stars?
Type A is their spectral classification.
Basically, when you look are a large number of stars with a spectroscope, patterns will develop and stars can be classified into different types.
The main types are:
O, B, A, F, G, K and M
O are the coolest and M are the hottest.
This can be easily remembered with the mnemonic "Oh, Be A Fine Guy/Girl, Kiss Me"
For more, read:
en.wikipedia.org/wiki/Stellar_classification

Going back to the beginning, instead of using Vega, let's say I try and use Bellatrix - a nice bright star in Orion.



If you compare this chart to the first one for Vega, you will see that the graph is much smoother - not as many spectral lines to calibrate our system.
Because Bellatrix is a Type B star, many of it's spectral lines are beyond the range of the camera to detect.
Therefore, it's not the best star to calibrate with on day one.

If we use the calibration data we used for Vega and get the spectrum for Bellatrix taking into account of the camera, the spectrum for Bellatrix will look like this:

I have inserted the Hydrogen Balmer lines for comparison.

If we overlay the standard spectrum for a Type B star, we get this:


Note how many of the spectral lines are located to the left of our red curve.
i.e. we can't detect them.
Compare that to the one for Vega we had earlier

Hopefully this demonstrates the difference between different star types and why we need to use Type A stars initially to calibrate our system.

Michael, would that work on a comet ?
Would it give you an idea about what its made of?

It sure would.
www.astrosurf.com/~buil/comet/lovejoy/obs.htm
This link is also worth looking at:
www.rspec-astro.com/sample-projects/#comet


and for some light-hearted test results:
www.astrosurf.com/~buil/liquid_spectro/result.htm

One of Betelgeuse for comparison.
It's a Type M star



Calibration curve from the library shown in blue.

Impressive Michael!

I did a spectroscopy project a few years back (2005) getting spectra of various star types. My setup was a lot less elegant though