Solar Spectroscopes - Are These Any Good?

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marktownley
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Solar Spectroscopes - Are These Any Good?

Post by marktownley »

At my recent day at keele uni, the guy who makes these was present and demonstrating his products...

http://www.elliott-instruments.co.uk/index.html

I thought they were pretty cool, and (for me) was interested in their Digi Spec http://www.elliott-instruments.co.uk/digispec.html as a possible tool for solar outreach that offers better results than a simple 'cd' spectroscope...

I would be particularly interested in views from those of you who 'know' about spectroscopes - i'm just a noob in this field...

Thanks,

Mark :)


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Re: Solar Spectroscopes - Are These Any Good?

Post by Merlin66 »

Mark,
It would certainly work and give low resolution (20A) displays....
To me it looked like a fixed slit, transmission grating (or maybe a three prism Amici) and a webcam combo....
You could assemble one for much less than 650gbp!!!
A star analyser grating 85gbp
A slit from two pencil sharpener blades 3gbp
A short length of PVC tube 2gbp
and a 25/80 or 25/100 achromat from Surplus Shed 8gbp
add your DMK or webcam and you'd get as good if not better results!


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Re: Solar Spectroscopes - Are These Any Good?

Post by marktownley »

Music to my ears Ken! I was hoping that is what you would say ;)

Do you have a schematic / drawing you could share to show how would be fixed together? I would probably get a colour webcam rather than my mono DMK so easy to see colour / wavelength relationship.


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Re: Solar Spectroscopes - Are These Any Good?

Post by Merlin66 »

Rusty,
Yes but....
It's even simpler for a star spectroscope - the star is already at infinity and presents a collimated beam to the transmission grating.... all you need is the grating mounted in front of the lens(PL2) and the lens (PL2) focused on the CCD chip. You then have an "Objective Grating" set-up.
To improve the clarity and resolution you really need to add a slit and a collimating lens (PL1).
Replace the "star" in your diagram with a slit and place it at the focus of your telescope you then have a "slit transmission grating spectroscope"
To get best results you need to take into account the deviation angle of the spectrum leaving the grating (around 3 degree per 100 l/mm) - the CCD should then be tilted relative to the grating by that amount.
Hope this helps.


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Re: Solar Spectroscopes - Are These Any Good?

Post by marktownley »

So, ken, is there a simple design you could point me to I could make? Would putting a colour webcam on the end of the one appollo has listed work?


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Re: Solar Spectroscopes - Are These Any Good?

Post by Merlin66 »

Mark,
The OPL is a very basic direct vision grating spectroscope, I don't know the slit details but it should work with a webcam ( with it's original lens fitted - to focus on the slit)
http://www.iceinspace.com.au/63-339-0-0-1-0.html
This is a Classical design - you don't need the guide part for solar...
A slit, collimating lens, grating, imaging lens and CCD
The slit can be as simple as a couple of pencil sharpener blades
The lenses from a cheap pair of 30mm binos -Lidl/Argos etc
A 300 or 600 l/mm grating would work well.(Optometrics)
and any available CCD camera (or webcam -minus the lens)
The Watkis (ex-BAA) is a compact transmission grating version (Paton Hawksley UK)
I have a drawing somewhere which I'll upload.
(Shameless plug: All these and much more are covered in my book "Astronomical Spectroscopy for Amateurs")


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"Imaging Sunlight - using a digital spectroheliograph" - Springer
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Re: Solar Spectroscopes - Are These Any Good?

Post by marktownley »

Thanks Ken, I will have a good read of it...


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Re: Solar Spectroscopes - Are These Any Good?

Post by Merlin66 »

mark.
I've found the original BAA article on the simple Watkis design, but I'm having problems logging on via my XP machine (I can't upload files from this Win7 PC). Bear with me, I'm sure it will come good soon.......


"Astronomical Spectroscopy - The Final Frontier" - to boldly go where few amateurs have gone before
https://groups.io/g/astronomicalspectroscopy  
http://astronomicalspectroscopy.com
"Astronomical Spectroscopy for Amateurs" and
"Imaging Sunlight - using a digital spectroheliograph" - Springer
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