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Spectrography - How to start?

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cmorsoc
cmorsoc's picture
Spectrography - How to start?

Hi, I'm Carlos Morales, I joined AAVSO 8 months ago and I've been learning as much as possible!! And now, I'd like to start with Spectrography. Could you please let me know how to do it? Do you know an online course about it? Any tip will be great!

THANKS A LOT!

Carlos

Ken4optics
Spectroscopy 101

Carlos,

Spectroscopy, like AstroPhotography (AP) is a large and diverse subject.

Like choosing the right gear for AP, you need the right gear to suit the aspect of spectroscopy you want to follow. 

You need something - a grating or prism to produce a spectrum from the target. The spectrum is then processed to allow it to be analysed.

Like telescopes, we define a spectroscope by it's resolution - the ability to separate features in the spectrum, this is the R value.

 

Let's consider two aspects:

1. Low resolution R= 300 (>15-20A) - this can be achieved with a simple transmission grating (SA100 or SA200) mounted within your telescope at a suitable distance in front of your CCD camera. This technique will allow you to record the spactra of the brighter stars (for comparison) and with longer exposures possibly nthe spectra of novae and SN as well as quasars(!). But it relies on staller images and not suitable for extended objects like the moon, planets etc.

2. Using a slit spectroscope allows you to control the resolution and some can achieve > R=10000 (<0.1A), but at a $$$ cost and increased complexity - slit guiding, reference lamps and effective tracking to allow exposures beyond many minutes.

The Shelyak ALPY, LISA and LHiRESIII are examples of these instruments.

Then there is the "issue" of processing the spectral image into a calibrated 1D profile to allow further analysis. Thankfully there are many freeware software packages available to the amateur (BASS Project, VSpec, ISIS etc)

There's a steep learning curve, but belive me the end results justify the pain.

SUMMARY

I'd recommend  starting with a SA100/200 grating to acquire your first spectra, then try one of the available packages for processing (Spectroscopy 101)....

(Tom Field in the US distributes the SA100 and his commercial software RSpec - he has some neat introductory video's you'll find helpful.)

Also, Robin Leadbeater, the developer of the Star Analyser, as a great webpage which will guide you.

There's some dedicated forums for amateur spectroscopy which I'm sure you will find on Google.

Any questions let us know.

 

 

 

 

 

cmorsoc
cmorsoc's picture
Spectroscopy 101

Thanks a lot.

Carlos

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