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Spectroscopy -Why no takers??

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Although I know very little about stellar spectroscopy (sad really as I suppose I am a spectroscopist by training) it is something I would really like to have a go at - I do have some assorted junk kit from a spectroscopy lab and I may have a play with that. Hopefully, there will be a more developed interest in the subject on SGL so I can learn more!

By the way, I have seen some very pretty stellar images through an objective prism that are stunning to look at....


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Spectroscopy......the dark art (or science) that takes light and splits it up in to its individual wavelength components. By doing this we can work out by seeing what spectral lines are there and are

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Thanks for the comments/ support and feedback.

There's a couple of "basic" books I'd recommend (unfortunately out of print but available on Amazon/ Alibris etc)

- "Practical Amateur Spectroscopy" by Steve Tonkins

- " Stars and their Spectra" J B Kaler

- " Spectroscopy: The key to the stars" Keith Robinson

There's also a new book coming out in Jan,:)

I agree the Star Analyser (SA100) is an ideal, low resolution, starting point.

It allows you quickly get a collection of stellar spectra which will show you the differences in the stars (classification), planetary nebula (emission spectra), and doppler shift of quasars (Redshift)

Torsten Hansen is doing some excellent work with a SA100 and a DMK camera on a 8" Newt.

I've been concerned about the quantum jump in complexity (and cost!) in making the move to a slit spectroscope which can be used for high resolution spectroscopy (<0.05A). The commercial units from SBIG, Shelyak and Baader start around $3000 (Ouch!). So I designed and manufactured a "Spectra-L200" Kit which I've made available through the Y! Group Astronomical_Spectroscopy for less than $900. This at least allows the amateur to grow and develop in the science.

I'll post a couple of SA100 spectra which you may find of interest...

One shows a neat little planetary NGC 7026 (which I'm 100% sure will be in your image of the NA nebula...but have you seen it??) It shows up in all it's glory in a 150s exposure using a 85mm camera lens

The other is a comparison of a modded Canon v's a non-modded version, Vega spectrum which clearly shows the results.

Spectroscopes can also (as Rick has shown previously) be used to test and demonstrate the bandwidth etc of any filter. No more guessing..

I can't do better than quote from Sir William Huggin's (He went on to design, build and use spectroscopes for the next 40 years!)

“I soon became a little dissatisfied with the routine character of ordinary astronomical work, and in a vague way sought about in my mind for the possibility of research upon the heavens in a new direction or by new methods. It was just at this time ... that the news reached me of Kirchhoff's great discovery of the true nature and the chemical constitution of the sun from his interpretation of the Fraunhofer lines.

This news was to me like the coming upon a spring of water in a dry and thirsty land. Here at last presented itself the very order of work for which in an indefinite way I was looking -- namely, to extend his novel methods of research upon the sun to the other heavenly bodies. A feeling as of inspiration seized me: I felt as if I had it now in my power to lift a veil which had never before been lifted; as if a key had been put into my hands which would unlock a door which had been regarded as for ever closed to man -- the veil and the door behind which lay the unknown mystery of the true nature of the heavenly bodies”

Edited by Merlin66
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Sorry to ask a really stoooooooooooopid question, but is the Paton Hawksley Star Analysers all you need? Screw it in like a filter, take some shots thru a webcam and you're up and running in spectroscopy?

Is there any other hard ware needed? Is there any special software required, where from and is it free?

If the answers are yes, no, yes, here, yes then I can see a lot more people getting involved! (me included!)

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Sorry to ask a really stoooooooooooopid question, but is the Paton Hawksley Star Analysers all you need? Screw it in like a filter, take some shots thru a webcam and you're up and running in spectroscopy?

Is there any other hard ware needed? Is there any special software required, where from and is it free?

If the answers are yes, no, yes, here, yes then I can see a lot more people getting involved! (me included!)

Damn, I was hoping for; yes, yes, no, yes, here, yes :D

Must be the spectral lines shifting :)

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I have met spectroscopy on courses and, of course, found it brilliant. That data is where all the real information is. Similarly on a Jodrell Bank course I participated in a suvey of the Milky Way in the 21cm band, looking for doppler shifts indicative of the presence of spiral structure. When you actually find it and try to map out the arms the buzz is incredible.

But I think that the key is to have a project. Rather than asking Ken about the technical side I'd first be more interested in what he sets out to do in his work.

Projects, lines of enquiry, etc etc.

Back on imaging, there is no doubt that the term 'pretty pictures' is either self deprecating or mildly disparaging, depending on who is sayng it. I live with an artist who paints landscapes. Should we condemn these paintings because they contain no useful geology, botany, meterology, cartography or survey trigonometry?

Did Rembrandt set out to produce pretty pictures? Or Goya? Or Velasquez?

Let me be dead clear about this, I set out to produce beautiful pictures celebrating the staggering beauty of nature. I also want them to make underlying physical processes visible. And I want, as Martin said, to bring this to public attention.

Now I don't claim to have succeeded, that is another matter. But 'pretty pictures' is not my game, not that anyone on this thread is directly saying that it is. Science, however, does not own the night sky. Art also has something to say about it and that is where the imagers step in.

I like it all.


Edited by ollypenrice
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Yes, yes, Yes!!

Just get a SA100 screw it into the nosepiece and take some spectra!!

Vspec is a freeware program which will allow you to display the spectrum as a 1D graphic and compare it with standard spectra...

Vspec - Download

Edited by Merlin66
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Excellent! That's the kind of answer I was hoping for. Thanks Ken, you might just have set me on the path.

I've heard that this new book out in January is the must have for spectroscopy. Any idea who it's written by, when it's released and where it can be bought from? Will the author be signing copies at all? :)

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Astronomical Spectroscopy for Amateurs : Ken M. Harrison : 9781441972385

It's also available through Amazon.....

The first image is Cygnus showing the emission from the 8.7 mag planetary NGC 7072.

Taken by Janet S with a objective grating.

The second is a spectrum of Vega; std Canon 350 v's 300D(modded-filter removed) by Jack Martin. The hydrogen Balmer series very visible.



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The only real impact is the loss of focus due to the chromatic aberration (CA). This may mean you have to re-focus between the blue and red end of the spectrum.

Remember the CFZ (Critical focus zone) - where you can't tell the difference in the point of focus is 0.141mm for an f8 system - which is probably as much as the CA!

(For faster systems ie f4 this is only 0.035mm - which is why it's so difficult to get absolute tight focus with some focusers)

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Olly and others,

I agree it's very satisfying to obtain good "beautiful" astro images...

I did it myself for almost 15 years!!

The equipment and skills used today to obtain these photographs is certainly very very useful, and can be applied to spectroscopy; I'm just trying to better understand what I could do to assist amateurs move across to spectroscopy...

There's three aspects of the work:

1. Collecting the raw data - spectra of designated objects using different telescopes and spectroscopes with the best SNR obtainable

2. Processing the data - usually corrections for flats/ darks/ camera response and wavelength calibration etc

3. Analysing the data - this can be done both by amateurs and professionals. You don't need a PhD in Physics, but you do need some rigor and discipline. There are many sources of comparison spectra to assist. The BeSS, the database on Be emission stars has over 20,000 spectra mostly collected by amateurs.

( I have a couple of high school students doing spectroscope projects - Broadening of the H Balmer lines with star classification etc)

Wouldn't you like to determine the amount of Sodium in Io's atmosphere?- the orbital period of a close binary star?? or the constitution of a planetary nebula??

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Ah, Jack Martin is the chap at Kelling, thanks for the name Ken :)

Great thread btw, very interesting stuff coming out. If imaging is the dark side, spectroscopy must be the work of Sith lords :D Im gonna stop reading this thread before I get too interested!

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Casually wondering if one can image spectra (as pretty pictures) in monochrome. I guess one could use a similar technique to RGB(L) imaging? Sadly, I sense my new QHY filters leave a nice big GAP, precisely to exclude Na (vapour) light pollution... :)

Edited by Macavity
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99% of all the spectra images are taken with monochrome cameras.

This gives maximum resolution and usually these cameras have a good camera response curve. My favourites are the trustly MX916 and the ATik16ic.

Once you have calibrated the spectrum in wavelength Vspec can provide a "Colorised version" for the Pretty Picture competition:rolleyes:

"No filters were damaged in the making of this spectrum"

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Hi all,

I have been doing spectroscopy for about 6 months now and its dead easy to do!

Ideally you want a telescope with a piggyback setup for guiding

but I have successfully managed to do high resolution spectroscopy with a c14 on a CGE mount without any guide scope at all!. You just need a reasonably good polar alignment.

To start with you can use a star analyser for 100 quid and get

spectra of stars and galaxies.

You can obtain higher resolution spectroscopes from a number

of sources with prices starting well under £1k

The number of projects you can do with them is basically infinite

- its only limited by your knowledge of stars and astronomy

And if you don't want to do your own projects you can join

some projects out there - example is the epsilon auriga project

where you can send in spectra of this star which will be recorded

along with the others and there is a yahoo group so you can see

regularly what the other amateurs are doing and also what

the professional astronomers studying this star are getting up to.

Over 75% of what we know about astronomy is through

spectroscopy its a whole world out there waiting to be discovered.

Personally I get bored after looking at the same old messier and arp objects again and again. I am on a personal mission to understand more about astronomy and the cosmos we live in and one of the best ways of doing this is through spectroscopy.

See my blog to see what I am up to and I have an album with some spectra I have taken.

I am happy to talk to anyone about the subject - you can post me in private if you want to talk



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Crikey... I know you must be as clever as a man with 2 heads! :)

Thanks for the explanation BTW.... well set out...


Spectroscopy......the dark art (or science) that takes light and splits it up in to its individual wavelength components. By doing this we can work out by seeing what spectral lines are there and are not there what physical processes are going on within the object being studied.

There are basically two kinds....low resolution, and high resolution. Resolution means in this sense how much we zoom in to the spectrum. A low resolution means each pixel sees a wider range of wavelengths, maybe around 1nm, whereas high resolution would be maybe 0.1nm or less. Imagine taking light from a star and throwing it in bins according to its wavelength (or energy). A low resolution would mean less bins, and so each bin would see more light being thrown at it. This leads to a high signal to noise but less detail. High resolution would mean lots of bins, but each bin wouldnt get a lot of light, leading to lots of detail but poor SNR.

Whether you use high or low res depends on what you want to see.

What objects are interesting spectroscopically....?? Well the sun for a start, but really you need high res: definitely looks better. You will see plenty of spectral lines, all of which have been identified and wavelengths accurately measured. If you had a very high resolution you could resolve the doppler shift of spectral lines as a result of the suns rotation. You could then tell how fast it rotates...

The most obvious application is in stars. It was Josef von Fraunhofer who first realised that spectral lines seen in the lab were also present in stars. This is when astronomy became astrophysics. There is a classification of stars based on the spectral lines...its the well known Harvard scheme. You know OBAFGKMRNS....'oh be a fine girl/guy, kiss me right now sweetie'. So when people say that the sun is a G2 star...the G comes from the harvard scheme. So you could take a stellar spectrum, look for the lines, give it a classification, fit a blackbody curve to it and estimate the temperature. From this you could estimate the mass of the star. You can actually measure the photometric properties of the star too, by applying a filter curve, like a johnson filter, to simulate the signal you would have recorded had you placed that filter in the light path in front of your CCD. You can workk out the B-V and U-B magnitudes and plot a diagram called a hertzsprung russell diagram (or colour-colour diagram to be exact). This tells you more information, and can infact tell you this distance to stars, or age of star clusters if you pick stars from the one cluster, eg, double cluster, or a glob like M13.

Certainly stars are the obvious choice of things to look at spectroscopically, and there is much to learn. This is best done with a broadband filter as you would want to cover the range of 400-800nm (or more) ideally. Certain kinds of stars have interesting kinds of spectra, for example P Cygni stars show doppler broadened lines resulting from stellar winds. And Be stars show hydrogen emission lines! Unusual for a star.

Then there are nebula....again two types....reflection, which is just reflected starlight, or emission (planetary neb, supernova's and HII regions). These emit light at discrete wavelengths, based on the temperature of the ionising radiation source (usually a white dwarf or hot young stars) and the elements present. Here it is interesting to know what elements are present and the temperature of the central region, and this you can determine using what astronomers like to call spectral line diagnostics. The ratio of certain emission lines is a function of temperature...if you measure the ratio through spectroscopy, then you can infer the temperature required to produce that. This again only needs low resolution.

From a personal point of view either stars or emission nebula would be interesting.

If you want to get very advanced, you could try to measure hubbles constant :) Hubble observed that the further away a galaxy is the faster it recedes from us. How fast? Well measure its spectra. You will see the lines redshifted slightly (it will be a small amount). The Ha line is probably the best to use. Using a bit of astronomy you can work out how fast the galaxy must be going away from us. Low resolution means that a high velocity is required, which means the galaxy must be far away and is hence faint.... a res of 0.5nm at Ha would imply that the nearest galaxy where redshift could be detected would be...dw/w = v/c, where w is wavelength...about 11 Mlyr.

There are two kinds of spectrometer I have used...the Paton hawksley star analyser, which is low res. This is a screw in type. But...thinkabout seeing. as the star twinkles, so will the spectrum which will smudge your spectrum. But its cheap

There is a LHiResIII, which is much more professional, and because it works using a slit, you always get the promised resolution. You can get different gratings as well, the hi res one is great for the sun. Astonishing. I would be tempted with a low res grating, since it means you get a much better SNR...really needed for this sort of work.

Hope this gives some more info...


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Thanks for your informative post, John.

Is it possible then to do any meaningful spectroscopy for a £100 investment (in addition to an existing imaging setup) or does one need any extra hardware or software?

Can this be attempted under light polluted skies or will the usual light pollution emission lines be evident as noise?

This looks like quite an interesting niche within the hobby, but I do agree with you that a lot of discoveries (indeed Hubble's famous discovery) was made via spectroscopic and not visual or standard imaging techniques.

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Thanks for your informative post, John.

Is it possible then to do any meaningful spectroscopy for a £100 investment (in addition to an existing imaging setup) or does one need any extra hardware or software?

Can this be attempted under light polluted skies or will the usual light pollution emission lines be evident as noise?

This looks like quite an interesting niche within the hobby, but I do agree with you that a lot of discoveries (indeed Hubble's famous discovery) was made via spectroscopic and not visual or standard imaging techniques.

The short answer is yes there is a lot of meaningful work that can be done with star analyser. But don't just take my word on it try the following sites and groups:

Star analyser user group staranalyser : staranalyser

Christian Buil's web page: Star Analyser spectrograph

Also robin leadbetters site http://www.threehillsobservatory.co.uk/astro/spectroscopy.htmyou will see that its uses include identifying supernovae types, detecting molecules in comets and measuring the redshift of Quasars.

and shlyaks web site:

Shelyak Instruments

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Spectroscopy is something that for me has always gone hand in hand with the enjoyable observing / imaging side of astronomy. But like all things it's horses for courses. Some like some don't. If we all liked the same aspect of astronomy it would make a dull forum. It's the diversity of interests that makes the forum exciting and provides us a high hit rate that somebody will have an answer to somebody elses question.

So lets all enjoy what we do, whatever the main area of interest and importantly lets learn things we don't already know because it can only benefit and enhance what we do know.



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  • 2 weeks later...

Hi, I'm the author of RSpec, the new real-time spectroscopy program mentioned earlier in this thread. As you might guess, I've given a fair amount of thought as to why spectroscopy hasn't caught on more than it has in the past five or ten years. Please forgive me for the lengthy posting below.

Here's my story: Several years ago, I bought a Star Analyser grating, expecting to have some fun. I didn't have fun. Even just capturing images was difficult because I couldn't even see if I was doing it right until the next morning when I post-processed the data.

And, the next morning? Total nightmare. I had to jump through four unrelated programs to convert my data (with no documentation explaining the process). The final program that I used to process the spectra, although justifiably very popular, wouldn't install, then installed but kept crashing erratically. Its manual was mostly translated into English, but seemed to be aimed at people who already knew spectroscopy.

I believe the biggest obstacle to wide-spread adoption of spectroscopy by amateur astronomers is that, up until now, the only software that has been available has been difficult to learn and use. (It’s also astonishingly powerful -- more so than RSpec will probably ever be.) Where I believe my software can make a difference is that because of its ease of use, it opens the door to newcomers. With RSpec and an inexpensive grating, you can learn the field and get fascinating results.

It was the frustration I experienced in my first attempts at spectroscopy that I led me to write RSpec. I wrote it for a selfish reason: I wanted a tool for myself that allowed me to do spectroscopy easily. The on-line spectroscopy community has been wonderfully supportive of my work. High caliber experts with skills and experience like Merlin66 have been very helpful in providing me feedback and suggestions. And the resulting software hopefully reflects that.

I've been writing software professionally for more than 25 years. I put everything I've learned over those years into the program: software engineering, user interface design, work-flow, multi-threading, tiered-complexity, software testing and QA, and, most importantly: user education -- i.e. how a new user learns.

RSpec comes with twenty on-screen video tutorials (a total of about 60 minutes' worth). They walk a new user step-by-step through the process of capturing and processing a spectrum. If you have a camera of any sort, with RSpec and a properly mounted SA grating you can capture a live spectrum on your first night out... guaranteed! It's quite exciting!

I'm proud of RSpec's user community. I think it demonstrates that with the right software and educational materials, anyone can learn spectroscopy if they’re interested. For example, there's a 75 year-old man in Oregon, who had never done spectroscopy until two months ago. He is now at the intermediate level and asking all the right questions! And he's so darned excited about what he's learned that his enthusiasm is contagious.

The amateur spectroscopy community has been well-led by the path-breaking work of the European community. For instance: Robin Leadbeater developed the Star Analyser and published some remarkable results on his website. The French developed a wide range of tools and techniques: from software to hardware, including the wonderful $3,000 LHiRes III spectroscope. (They're now doing research-quality observing, contributing to professional efforts.) Our Merlin66 here has created an intermediate resolution spectrometer. And he has has written a book that we're all looking forward to owning in a few weeks. :-)

The other major obstacle to more amateurs getting involved in spectroscopy is the myth that it requires dark skies, large aperture, near-professional skills and a PhD in physics! That all might have been true at one time, but, these days, there are tools and community that make it relatively easy, as the 75-year old mentioned above discovered.

No, spectroscopy isn't for everyone, as noted earlier in this thread. Some amateurs aren't interested in graphs and data, preferring the aesthetic beauty and accessibility of visual imaging. However, there remain a large number of amateurs who would like to collect objective data with their gear, but are intimidated by spectroscopy because of the perceived difficulty. I think that the time is ripe for them to get involved in spectroscopy.

But don't take my clearly-biased word for it. The RSpec site has lots of videos, examples of sample projects, and a free, fully-enabled trial version of the software. If you're being held back by your wallet, or lack of equipment, knowledge or weather, then the site has a sample .avi video file that you can download so you can immediately start experimenting with spectroscopy. I invite you to try it out. And then post back here or email me with your results!

Personally, I've found that getting involved in spectroscopy has enormously deepened my understanding and engagement in astronomy. Once you're doing spectroscopy, you tend to read the available literature (Astronomy Now, Sky & Telescope, etc.) with a much better eye. Things that you formerly skimmed you're now reading and actually understanding! There's nothing more exciting than new knowledge.

Thanks for the opportunity to share my opinion.

Of course I welcome any feedback.

Tom Field


Edited by tom--rspec
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