Archive for the ‘Spectroscopy’ Category

Aldebaran Spectrum

Posted: November 2, 2011 in Spectroscopy, Stars

I’m determined to master the spectroscopy thing by the Spring.  Here’s a heavily processed image of the spectrum of the star Aldebaran in Taurus that I got at the observatory last night.

It’s very low resolution – I couldn’t get the distance from the Star Analyser to the Meade DSI II camera big enough to really bring out the absorption lines clearly.  I think I’ve figured out how to do it next time.  Nevertheless, you can see some dark bands in the spectrum.

Here’s a profile of the brightness along the middle of the spectrum.

The scale shown for wavelength is extremely rough and ready!  The troughs of the graph correspond to places where particular wavelengths of the light have been absorbed by the atmosphere of Aldebaran or by our atmosphere.

Aldebaran is an orange giant star; the star is off the main sequence because hydrogen fusion in the core has stopped.  It has swelled into a giant star with a cooler orange “surface”.

The next step for me is to consistently be able to set up with a higher resolution and then calibrate the resolution it using a well known spectra (i.e. Vega).

All good fun!

Absorption lines at last!

Posted: January 19, 2011 in Spectroscopy
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I’ve been trying to crack this spectroscopy for a while now.  I set the scope up outside the back door and spent some time aligning it.  

Rather than spend £8 on a spacer to increase the distance between the SA100 and the DSI chip, I’ve dismantled a couple of my colour filters – carefully removing the glass – and used those instead.  Plugging the whole thing into the Celestron NexStar 102 and sorting out some problems because of the new focus distance – I slewed the telescope around to Betelgeuse.  Immediately I could see an improvement over last time!
The blazed first order spectrum showed some detail.  I tried several other stars: Rigel, Aldebaran and Mintaka.  I couldn’t see any obvious lines on Rigel and Mintaka.  I’ll process them all tomorrow to see if I got anything.
I stretched the Betelgeuse line spectrum into a band:
and tried to identify the absorption features.  This is what I think is on there:
The image on the chip still doesn’t seem big enough.  I’ll try and figure that out when I’m less tired.  Surely not more spacers needed – I’m using three already!  After that I’ll have to calibrate the system so that I can measure the wavelengths of absorption lines and identify them in a less haphazard way,