Spectroscopy - Getting Started?

[Shark Bait (Stu)]

I have been getting up in the mornings to check in on Nova Cen 2013 whenever clear skies have allowed. It has been interesting watching the changes using both unaided eye and 7x50 binoculars. Trying to work out its apparent magnitude by comparing the nova to nearby stars has added another layer to visual astronomy.

I have read the current threads showing spectra and am now interested in getting involved in spectroscopy. Bintel sell a specialised filter and a book that covers stars and their spectra, although it may not cover how to get started from scratch.

What is the minimum setup to get useful results as shown by current nova posts?

Software requirements, cameras and good books that decode what the data shows?

Stu.

[Merlin66 (Ken)]

Stu,
My books from Amazon (see below) cover all the basic stuff you need to know about TAKING spectral images and basic processing.
Interpretation of the data is a much more complex learning experience!!
Kaler's book is a great starting point.
All you need to start is a grating (Star Analyser/ Rainbow Optics) a telescope f5 or above and a CCD camera...cooled mono preferred.
This will allow you to collect spectral data on thousands of stars, nova etc. etc. These lo-res spectra are great for learning your way around the basics of processing spectra (darks, background removal, wavelength calibration and instrument response.) Later you may consider moving up the "food chain" and investing in a slit spectroscope which, although more complex to use, can provide very useful detailed data for other amateurs and professionals.
I recommend looking at our Yahoo group:
http://groups.yahoo.com/neo/groups/a...ctroscopy/info
for more details (check out the files area) on spectroscopes (DIY and commercial) and basic methodology.
Hope this helps.

[malclocke (Malc)]

Hi Stu,

I'm a beginner in this field, so definitely take the advice of the more experienced here above mine.

The standard first step is a Paton Hawksley Star Analyser SA100 - http://www.patonhawksley.co.uk/staranalyser.html. Even if you end up moving up to more advanced equipment, you will still probably use an SA100 once in a while, so this is a no brainer. The SA100 is very basic, it is a diffraction grating mounted in a standard 1.25 inch filter holder. The grating contains many fine parallel lines (100 per mm) which cause any light shone through it to diffract into a rainbow. Currently costs 92.70 GBP.

The SA100 is designed to work with a camera, as opposed to be used visually. It will work with a DSLR, but you will get the best results with a mono CCD. It is somewhat counter-intuitive, but you don't need a colour camera to take spectra. I use a mono QHY5 guide camera, others use proper mono CCDs.

The SA100 is most commonly used in a telescope, basically threaded into the camera nose piece. However you can also use it to great effect with a DSLR lens. See Rob_K's excellent results on the nova thread.

Using an SA100 will get you acquainted with processing spectra. The standard free tools are VSpec (http://www.astrosurf.com/vdesnoux/) and ISIS (http://www.astrosurf.com/buil/isis/isis_en.htm). There is also RSpec (http://www.rspec-astro.com/) which is not free.

Ken's book 'Astronomical Spectroscopy for Amateurs' is an excellent introduction to how to take and process spectra. There is a great section on processing an SA100 spectrum with VSpec.

A great free PDF book is Richard Walker's Spectroscopic Atlas (http://www.ursusmajor.ch/astrospektr...-walkers-page/). This shows examples of various spectral types and explains some of the features you will see when you start taking your own.

To understand some of the theory behind spectroscopy, I found 'Spectroscopy - The key to the stars' by Keith Robinson (http://www.springer.com/astronomy/as...-0-387-36786-6) a fantastic read. Most books on quantum theories touch on matters related to spectroscopy too, the two are tightly linked.

I think it's kind of like marmite, some amateurs just don't see the appeal. Others, once they've had a taste, just can't get enough of it!

[Shark Bait (Stu)]

Thankyou Ken and Malc. The information provided is appreciated and I will follow up on all of your links.

Stu.

[Jon (Jonathan)]

Stu, I second to the letter everything Malc has written.

Ken's book on gratings is a great book to start from a practical point of view. Keith Robinson's book on spectra and stellar physics is at the top of my astronomy book list even for someone who ISN'T interested in the practicalities of taking and processing spectra.

The other good news is, all you need to start is a camera and a star analyser. I confess got some if my best SA100 spectra by sticking it to the front of a DSLR with a bit of Blu-Tak. With nothing more complicated than that I was able record the methane absorption bands in the atmosphere of Uranus.

Malc's comment about Marmite is spot on. If you think about it, amateur astronomy focuses on nebulae, planets, galaxies, comets - everything except the stars themselves. In the end, stars are just static points of light, not very interesting. The thing about spectroscopy is that it allows you to "see" the fascinating and dynamic activity within stars - the thermonuclear reactions driving them; the shells of gas they blast into space and then energise, at a measurable fraction of the speed of light; the whirling dance of a red giant orbiting a white dwarf every two hours, bleeding hydrogen onto an accretion disk. Spectroscopy is, literally, where you get to see the action.

All for a $175 star analyser. Best value for money in the whole hobby, IMHO.

[Rob_K]

Originally Posted by Jon

If you think about it, amateur astronomy focuses on nebulae, planets, galaxies, comets - everything except the stars themselves. In the end, stars are just static points of light, not very interesting. The thing about spectroscopy is that it allows you to "see" the fascinating and dynamic activity within stars - the thermonuclear reactions driving them; the shells of gas they blast into space and then energise, at a measurable fraction of the speed of light; the whirling dance of a red giant orbiting a white dwarf every two hours, bleeding hydrogen onto an accretion disk. Spectroscopy is, literally, where you get to see the action.

All for a $175 star analyser. Best value for money in the whole hobby, IMHO.

[Shark Bait (Stu)]

Great to hear your thoughts on Spectroscopy Jon and Rob. Thankyou. Moving from simply observing the night sky to having a deeper understanding of what a stars light can tell us is a large part of the appeal.

Nova Cen 2013 (my first) has left me wanting to do more. It is no longer enough to estimate the magnitude and colour.

[Merlin66 (Ken)]

Astronomical Spectroscopy - The final Frontier - "to boldly go were few amateurs have gone before."

[Gasman]

Hi guys
Not posted for a long time!. I too can vouch for Ken`s excellent books on the subject and have all of them on my bookshelf!. I have just received another superb book new from the Springer stable by Jeff Hopkins `Using Commercial Amateur Astronomical Spectrographs` which covers everything in minute detail for the amateur. One of the chapters describes a `DIY` spectrometer based on a reconditioned medical spectrometer from the States which I am eagerly awaiting after finding one on ebay!. There is also an excellent chapter on Rspec which could serve practically as a user guide on it, highly recommended!!
Merry xmas to all on the forum
Steve