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Merlin66

Spectroscopy -Why no takers??

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I was reading the latest Messenger magazine from the ESO and noted that of the suggested instrumentation and projects for the E-ELT ( European-Extremely Large Telescope) that 90% of them involved spectroscopes.

Why is it then, while the professionals use spectroscopes for 90% of their research, that amateurs find it so difficult?

I'm surprised that more amateurs don't take up the challenge....

Is it the lack of the "Ohh Ahhh" astro-photo impact? Fear of the maths? or what???

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hi merlin...

I guess it is the lack of pretty pictures....

Plus most dont have the physics/maths skills to interpret what physical processes the various spectra indicate.

I think its very interesting though....and have considered trying it.

most folk dont care about the science

paul

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I am interested and have one of the Paton Hawksley Star Analysers, but the problem I have is that I'm interested in imaging Lunar, planetary, solar, deep sky and observing all of those which with the number of clear nights we have then I'm afraid spectroscopy takes a back seat. I also don't see that I can take it very far as I cannot afford a decent spectrometer. I have a physics background so it could be quite appealing.

I think I am a classic case of Jack of all trades but .......... but the main thing is I am getting much enjoyment out of the hobby.

Dave

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Well, I'm waiting for one book to be published :) Now I have star analyser, but I'm looking at getting something more advanced, slit based with guiding so snapping a spectrum of selected part of the planet would be possible etc. Regular spectroscopes of that type are expensive so - they aren't popular.

On the other side I use various filters to catch specific part of the spectrum like methane band on gas planets or 1010 nm band on Venus with RG1000.

And the software like VSPEC isn't perfect. I've got links to RSpec but not used it yet.

Edited by riklaunim

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Just bought a Star Analyser 100 too - Thus far, the only targets have been distinctly terrestrial. I'm hoping to do something with (Watec) video. Plenty of image brightness available? But I sense getting good resolution might be a challenge? Might be a tad more exciting in colour too... :D

'Pour encourager les autres'? :)

STAR ANALYSER 100 USER MANUAL

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I guess the number of amateurs active in scientific observational astronomy has grown far more slowly than the number of people involved in the wider hobby. Affordable scopes, goto, digital photography and access to information via the internet has made astronomy far more accessible than when I was a boy struggling with a Dixons 60mm refractor.

Lets face it, traditional astronomy had a high geek quotient. Observing variable stars is not everyone's idea of a cracking night out.

I confess a deep ignorance when it comes to amateur spectroscopy. What are the opportunities, what does it involve and is it expensive? Is there an opportunity for a an SGL members project?

I suspect that Paul mentioned the lack of pretty pictures with a slight sneer. I make no apology for being into pretty pictures and the challenge of capturing them. OK, I wont be making any contribution to the scientific understanding of the universe but I am creating an increased awareness of what is out there beyond planet earth.

most folk dont care about the science

paul

I think most people on this forum do care about science Paul regardless of their level of scientific educational attainment. You will find pseudoscience gets very short shrift on here.

I think its very interesting though....and have considered trying it.

paul

Well don't just consider it, do it! :)

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Martin...that wasnt said with sneer. I am an imager. This isnt obvious?

Thats why I do astronomy....pretty pictures. And why would I have spent several thousand on imaging kit, if I thought it was a silly thing to do?

ally and I are forever telling everyone doing astronomy up here in glasgow to go out and observe and image the things they learn about.

well give people a choice between seeing a picture of the rosette nebula and a picture of its spectrum, and what would they rather see? Thats why people image more than they do spectroscopy/photometry.

and I am sick of people assuming that they know anything about me.

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Spectroscopy has had a high amount of diy/atm activity involved in it, and probably still does. There are some commercial units, but the production is low volume and price is high. So you add that onto the cost of the scope and ccd camera, then you do need to be pretty enthusiastic.

There are a few experts in the uk - Robin Leadbetter, Maurice Gavin, Jack Martin to name but three - and there are probably a few more active observers. But I suspect not that many more...

Would be pleased to hear differently!

/callump

Edited by callump

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I know how much time and effort Kens put into this as well as his invaluable input on Solar mods...

I guess it either floats your boat or it doesnt...

Whilst spectroscopy has been useful in the day job over the years in an astronomical sense it doesnt do anything for me...

Billy...

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I'm surprised that more amateurs don't take up the challenge....

Is it the lack of the "Ohh Ahhh" astro-photo impact? Fear of the maths? or what???

Try googling 'define spectroscopy'. The wall of impenetrable science speak is quite off-putting! If someone were to explain spectroscopy in a way that regular astronomers (like me) can understand and relate to, things might be different.

I think it is a means of understanding what stars are made of, which is pretty cool... :)

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Martin...that wasnt said with sneer. I am an imager. This isnt obvious?

Sorry Paul, no offence intended. There is a rather high brow opinion amongst some of the upper echelons of amateur astronomy in this country that has a tendency to deride astro imaging for it's lack of scientific input. For a second I thought you had joined that set but delighted you are still "one of us" :)

and I am sick of people assuming that they know anything about me

Of course I know something about you, you wally. I don't know much about you and have to do a bicubic interpolation to fill in the gaps which isn't very accurate. Honestly, no offence intended :D

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So, Ken tells us more in plain English. Outlines some areas we might want to look into. FLO stocks some realistically priced kit and off we go with a project, sharing our data.

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So, Ken tells us more in plain English. Outlines some areas we might want to look into. FLO stocks some realistically priced kit and off we go with a project, sharing our data.

I'm up for it :)

Steve

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The other thing to note about spectroscopy is that you need (a lot) more photons than for imaging, so you are restricted to brighter objects. It's the same professionally of course, but there you have bigger apertures to play with.

NigelM

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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 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...

Paul

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That is really well written and described thank you. I always meant to go into astrophysics after finishing uni but money and growing debts dictated otherwise:)

£100, or even just under, to start, thank you :)

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Yes, many thanks Paul. I have saved a copy for future reference.

I like the idea of doing HR diagrams, but lets start first with some simple spectra.

Dave

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I usually camp by a certain Mr Bond at Kelling Heath. On his pitch are usually a white light solar scope and a solarmax 60 Ha solar scope. And his camping companion usually sets up a Spectrograph for people to use, with a chart for explanation. His sentiments are usually the same "why aren't people interested?" as most of the visitors give the spectrograph a wide berth or glaze over.

It just doesn't have the same pull for me as "normal" astronomy, either visual or imaging. I can't recall ever looking through a telescope or at a picture and thinking "hmm, I wonder what that star is made of?", and I guess that is the case for the majority.

Astronomy has a wide appeal, but certainly isn't mainstream, and spectroscopy appeals to a niche within that niche. Let's face it, most of us aren't in it for the minute scientific facts we learn. I guess more than a few here have been drawn into the hobby by the amazing amateur photos that can be seen on the www, I know I was.

I'm very glad somebody does it, and I hope they are very happy doing it, but apart from the casual glance at a star party, it isn't for me :D Pretty pictures all the way :)

Cheers

Tim

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I think a nice thing about spectroscopy is that it's truly cross-disciplinary? Back in the 70's, I was at a loss whether I wanted to be a "physicist" or a "chemist". I ended up hedging my bets by taking a "joint" degree. There was no custom courses, we simply rubbed along, alternately, with physicists and chemists. But "spectroscopy" was a big (fun) part in both syllabuses? The different departmental emphases were very useful though. ;)

Fortunately, in the rainy UK, the buildings were only separated by but a quiet, side street. But "culturally", even as students, there seemed to be quite a difference between the students. I admired the theory and precision of the physicists, yet found myself drawn to the aesthetics and application of the chemists. Heck, Chemists "had more fun" (LOL) - Or at least more female students and (consequently?) far better parties and discos! :)

These days, the division between the various sciences seem rather less. Heck, Particle Physicists even present (welcome!) popular programs on astronomy. A good thing, generally, I sense... :p

Aside: It's only very recently I had seriously wondered how the stellar spectral classifications were derived - It seems such a "given" in astronomy. Pretty much as I had thought, but I'd still like to know more details. :D

Edited by Macavity

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Heck, Chemists "had more fun" (LOL) - Or at least more female students and (consequently?) far better parties and discos! :)

When I was at sixth form I took Maths, Physics and Chemistry A-Levels. The Physics class was entirely male, the chemistry class mostly female and the Maths class a perfect 50/50 split.

I wonder why? Conditioning of some sort? I know the physics people were there contemplating some form of engineering degree, but why more female chemists?

Don't get that myself :D

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HI

I have followed this thread with intrest and although I know very little about spectrcscopy I am interested and have wanted to get into it for a while but been put off by the cost of equipment, I have learnt from this thread about the "Paton Hawksley Star Analysers" (thanks to Dave smith) so I,m really interested, I have contacted Paton Hawsey for more info and have downloaded the user manual (thanks for the link Macavity). I'm in the lucky position of having two scopes so I can do spectroscopy while imaging my DSOs.

Thanks all

Neil

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