K-Tec

Using a Star Analyser - Blog

  • michaeloconnell
  • michaeloconnell's Avatar Topic Author
  • Offline
  • IFAS Astronomer of the Year 2009
  • IFAS Astronomer of the Year 2009
More
3 years 9 months ago - 3 years 9 months ago #99644 by michaeloconnell
michaeloconnell created the topic: Using a Star Analyser - Blog
Some time ago, I bought a Star Analyser.
www.rspec-astro.com/star-analyser/
It is a diffraction grating which, to put it simply, breaks up the light from a star into its component colours and wavelengths.
I originally bought it around the time of Supernova SN2011dh in M51 in May 2011.
en.wikipedia.org/wiki/SN_2011dh
Dave Grennan generously loaned me his diffraction grating to try out first.
After giving it a go, I was intrigued and so bought my own.
After a few attempts at using it, it ended up in the bottom of my drawer until a few nights ago.
That's when I decided to dig it out and try using it with the software "RSpec".
www.rspec-astro.com/
This can be downloaded and tried out for a few weeks as a fully functioning demo.

When you attach the star analyser onto a camera and take an image of a star through a telescope, it is possible to determine the constituent gases in that star.
Likewise with planets. Below, in a series of posts, I will discuss how I started using it.
Last Edit: 3 years 9 months ago by michaeloconnell.

Please Log in to join the conversation.

  • michaeloconnell
  • michaeloconnell's Avatar Topic Author
  • Offline
  • IFAS Astronomer of the Year 2009
  • IFAS Astronomer of the Year 2009
More
3 years 9 months ago - 3 years 9 months ago #99645 by michaeloconnell
michaeloconnell replied the topic: Re: Using a Star Analyser - Blog
First step is to select a star.
It is recommended that the first star is Vega.
This is because it is a Type A star.
More on star types later....
Below is a output from the software Rspec of the spectrum for Vega



below is a portion of the image from the CCD camera.



the graph shows a sudden peak on the left hand side and a gentle rise and fall on the right hand side.
Looking at the photo, you will see a bright star, which is the star Vega, and a line off to the right hand side, which is the spectrum of the star.
If you look closely at the spectrum, you will see some lines in it.
These are of interest to us as they reveal the material that is burning in the star.
The software RSpec is able to analyse the spectrum and determine what the lines in the spectrum correspond to.

Looking at the graph, the sudden peak corresponds to the bright spot of the star and the remainder of the graph corresponds to the spectrum line.
Last Edit: 3 years 9 months ago by michaeloconnell.
The following user(s) said Thank You: paddyman, mikematthews

Please Log in to join the conversation.

  • michaeloconnell
  • michaeloconnell's Avatar Topic Author
  • Offline
  • IFAS Astronomer of the Year 2009
  • IFAS Astronomer of the Year 2009
More
3 years 9 months ago - 3 years 9 months ago #99646 by michaeloconnell
michaeloconnell replied the topic: Re: Using a Star Analyser - Blog
Now, there are a number of problems with the graph.
1. It is not calibrated for any known wavelengths
2. It does not take into consideration for the type of ccd camera I have.

So, to resolve this I need to do the following:
1. Calibrate the image against a standard image from a professional telescope - there is a standard version included in the software library.
If I compare my image to the library image from a star like Vega, the software is able to calibrate my photo.
Below is the comparison:



My spectrum is in red while the library spectrum is in blue.
This tells us a few things:
1. My camera cannot see all the light from the star - this is due to the fact that any ccd camera can only see a certain range of wavelengths and the atmosphere of the earth may be blocking some light/energy from the star also.
2. Aside from that, they compare pretty well.
Last Edit: 3 years 9 months ago by michaeloconnell.

Please Log in to join the conversation.

  • michaeloconnell
  • michaeloconnell's Avatar Topic Author
  • Offline
  • IFAS Astronomer of the Year 2009
  • IFAS Astronomer of the Year 2009
More
3 years 9 months ago - 3 years 9 months ago #99647 by michaeloconnell
michaeloconnell replied the topic: Re: Using a Star Analyser - Blog
Next step is to calibrate my camera.
This is done by dividing the library spectrum into my spectrum.
Below is the result:



For comparison, the Hydrogen Balmer lines are overlaid, which show good calibration.
Last Edit: 3 years 9 months ago by michaeloconnell.

Please Log in to join the conversation.

  • michaeloconnell
  • michaeloconnell's Avatar Topic Author
  • Offline
  • IFAS Astronomer of the Year 2009
  • IFAS Astronomer of the Year 2009
More
3 years 9 months ago - 3 years 9 months ago #99648 by michaeloconnell
michaeloconnell replied the topic: Re: Using a Star Analyser - Blog
For the heck of it, I then tried Jupiter:



and Uranus



as you can see, significantly different composition.
this here shows the Methane present in Uranus' atmosphere:


FWIW, Uranus' blue color is the result of absorption of red light by methane in the upper atmosphere.
Last Edit: 3 years 9 months ago by michaeloconnell.

Please Log in to join the conversation.

More
3 years 9 months ago #99649 by mikematthews
mikematthews replied the topic: Re: Using a Star Analyser - Blog
Fascinating! Spectroscopy and star analysis is something I'd hoped to dip my toe into at some stage in the future. Thanks for sharing!

Please Log in to join the conversation.

  • michaeloconnell
  • michaeloconnell's Avatar Topic Author
  • Offline
  • IFAS Astronomer of the Year 2009
  • IFAS Astronomer of the Year 2009
More
3 years 9 months ago #99650 by michaeloconnell
michaeloconnell replied the 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.

Please Log in to join the conversation.

  • michaeloconnell
  • michaeloconnell's Avatar Topic Author
  • Offline
  • IFAS Astronomer of the Year 2009
  • IFAS Astronomer of the Year 2009
More
3 years 9 months ago - 3 years 9 months ago #99651 by michaeloconnell
michaeloconnell replied the 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: 3 years 9 months ago by michaeloconnell.
The following user(s) said Thank You: Fermidox, manic_dave

Please Log in to join the conversation.

More
3 years 9 months ago #99653 by manic_dave
manic_dave replied the 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.

Please Log in to join the conversation.

  • michaeloconnell
  • michaeloconnell's Avatar Topic Author
  • Offline
  • IFAS Astronomer of the Year 2009
  • IFAS Astronomer of the Year 2009
More
3 years 9 months ago - 3 years 9 months ago #99654 by michaeloconnell
michaeloconnell replied the topic: Re: Using a Star Analyser - Blog
Last Edit: 3 years 9 months ago by michaeloconnell.
The following user(s) said Thank You: manic_dave

Please Log in to join the conversation.

  • michaeloconnell
  • michaeloconnell's Avatar Topic Author
  • Offline
  • IFAS Astronomer of the Year 2009
  • IFAS Astronomer of the Year 2009
More
3 years 9 months ago #99666 by michaeloconnell
michaeloconnell replied the 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.

Please Log in to join the conversation.

More
3 years 9 months ago #99691 by albertw
albertw replied the 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/

Please Log in to join the conversation.

  • michaeloconnell
  • michaeloconnell's Avatar Topic Author
  • Offline
  • IFAS Astronomer of the Year 2009
  • IFAS Astronomer of the Year 2009
More
3 years 9 months ago #99694 by michaeloconnell
michaeloconnell replied the topic: Re: Using a Star Analyser - Blog
Al,
I'm quite surprised at how easy it is to use and the level of detail that can be captured with a relatively simple and low-cost device.

Please Log in to join the conversation.

  • michaeloconnell
  • michaeloconnell's Avatar Topic Author
  • Offline
  • IFAS Astronomer of the Year 2009
  • IFAS Astronomer of the Year 2009
More
3 years 9 months ago #99805 by michaeloconnell
michaeloconnell replied the topic: Re: Using a Star Analyser - Blog
The following user(s) said Thank You: michael_murphy

Please Log in to join the conversation.

Time to create page: 0.153 seconds
Powered by Kunena Forum