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Using a Star Analyser - Blog

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10 years 5 months ago #99650 by michaeloconnell
Replied by michaeloconnell on topic Re: 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.

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10 years 5 months ago - 10 years 5 months ago #99651 by michaeloconnell
Replied by michaeloconnell on topic Re: Using a Star Analyser - Blog
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.
Last edit: 10 years 5 months ago by michaeloconnell.
The following user(s) said Thank You: Fermidox, manic_dave

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10 years 5 months ago #99653 by manic_dave
Replied by manic_dave on topic Re: Using a Star Analyser - Blog
Michael, would that work on a comet ?
Would it give you an idea about what its made of?

www.skelligstarparty.com
Europe's Darkest Skies
Top 4 Locations in the world to Stargaze by Paste Magazine.

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10 years 5 months ago - 10 years 5 months ago #99654 by michaeloconnell
Replied by michaeloconnell on topic Re: Using a Star Analyser - Blog
Last edit: 10 years 5 months ago by michaeloconnell.
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10 years 5 months ago #99666 by michaeloconnell
Replied by michaeloconnell on topic Re: Using a Star Analyser - Blog
One of Betelgeuse for comparison.
It's a Type M star



Calibration curve from the library shown in blue.

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10 years 5 months ago #99691 by albertw
Replied by albertw on topic Re: Using a Star Analyser - Blog
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 :)

Albert White MSc FRAS
Chairperson, International Dark Sky Association - Irish Section
www.darksky.ie/

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