3D printed UVEX spectrograph

3D printed UVEX spectrograph

Postby Christian Buil » Mon Jun 19, 2017 12:25 am

Hi,

I made a 3D printed version of the UVEX spectrograph, a first for me. UVEX (UltaViolet Explorer) is a Czerny-Turner design
(see http://www.astrosurf.com/buil/UVEX/index.html). Here the actual optical definition:

Image

Low cost and light spectrograph (300 grams without the camera, 670 grams with an Atik414EX camera), no guidance system integrated, no slit at this stage (!)... designed to be operated only on small telescopes (apochromatic refractor, small Newton telescope). Some view of the first 3D printing prototype (more optimized version is coming, thanks Pierre Thierry and Franck Vaissiere for the help):

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The first light on a Kepler 200 mm f/5 telescope:

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(note use of a CMOS camera, a ASI1600MM cooled model).

A Vega spectrum by orienting the grating to capture the entire visible spectrum onto the ASI1600MM large CMOS sensor :

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The great advantage of the system is the high degree of achromaticity, which allows to capture a correct spectrum over a very broad spectral range (R = 700 approximately). It is also possible to orient the grating to optimize the observation of ultraviolet (the primary goal!). Nothing else is changed in the spectrograph (it is also possible to obtain a good spectrum of the infrared part with the same definition). Here the UV spectrum of Vega:

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A significant signal is detected down to 3200 A with an Atik414EX / 460EX camera, and from a city observatory - no an altitude observatory. The "lines" observed near 3200-3300 A are the stratospheric ozone (O3) Huggins band. It is the proof of a valuable signal detection, not a noise.

Another example, wide spectral range spectrum of beta Lyrae (Shelyak), and a high SNR close look of ultraviolet part :

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Same concerning CH Cyg star :

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(with my polluted sky, the absence of slit is here a real problem, but in a good sky, the result would be more correct in the UV).

A hot star, gamma Cas (note structure near 3200 A, i.e. ozone Huggins band):

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a more coldest star, gamma Cyg :

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Finally, a modest spectrograph for the discovery of spectroscopy and explore the domain, but with which it is possible to do some science and study regions of the spectrum rarely explored by the amateurs.

Christian Buil
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Re: 3D printed UVEX spectrograph

Postby Christian Buil » Tue Jun 20, 2017 10:42 pm

More spectra... alpha Cep :

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Deneb :

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P Cyg :

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More exposure added for the Vega spectrum, my actual record concerning "far" UV region exploration - the limit is here 3130 A :

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Some drawing of the next iteration (for cover wide spectral range from UV to IR by grating rotation) :

Image

Image

Christian
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Re: 3D printed UVEX spectrograph

Postby Terry Bohlsen » Wed Jun 21, 2017 1:27 am

Very interesting Christian.
I'd be quite interested in making one of these. What are the mirrors, grating and lens?
Terry Bohlsen
Armidale NSW
Australia
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Re: 3D printed UVEX spectrograph

Postby Daniel Dejean » Wed Jun 21, 2017 11:24 am

Hello Christian,
Superb and very interesting ! This could bring much more amateurs to spectro. What about the resistance of 3D printing material for such application (mechanical flexion) ?
Congratulation for this new step to decrease entry cost to spectro. Ready to help with my home printer if required.
Bon ciel.
Daniel
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Re: 3D printed UVEX spectrograph

Postby Tim Lester » Wed Jun 21, 2017 5:21 pm

Christian - you never cease to amaze us!

An excellent design for others to fabricate (with or without a 3d printer).
Have you considered an achromat for the cylindrical lens. I found this on the ThorLabs site:
ACY254-150-A: f=150 mm, 1 inch dia. cylindrical achromat, AR coating: 350-700 nm - $376.00 US
Possibly a bit expensive.

Tim
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Re: 3D printed UVEX spectrograph

Postby Joan Guarro Flo » Wed Jun 21, 2017 6:32 pm

Excellent Christian,

The Uves is simply fantastic. And its results are really very good, the graphics in the ultraviolet are really impressive.
It also seems very easy to build. For larger diameter telescopes, it would be necessary to integrate a guide system.
I think that it would also be possible to connect to a fiber optic guide module.

Cordialement, Joan.
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Re: 3D printed UVEX spectrograph

Postby John Paraskeva » Wed Jun 21, 2017 8:32 pm

Excellent work as usual. Thanks for sharing.

Interested to know what 3D printer and printer resolution was used.

regards
John
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Re: 3D printed UVEX spectrograph

Postby etienne bertrand » Wed Jun 21, 2017 10:26 pm

This specra are beautiful, Vega is perfect.
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Re: 3D printed UVEX spectrograph

Postby Michel Verlinden » Thu Jun 22, 2017 11:18 am

Bonjour Christian,
Un grand merci pour ce nouveau trésor technologique et le partage de ton savoir-faire, ils vont permettre de repousser les frontières de la spectroscopie en amateur (et quand je vois tes prouesses, notamment tes derniers travaux en spectropolarimétrie et l'observation de l'effet Zeeman dans les spectres d'étoiles, je me demande si tu n'as pas de limite !)
Dans ce type de spectrographe, doit-on s'attendre à des mélanges d'ordres ?
Comment calibres-tu les spectres avec un résultat précis dans le proche UV ?
Dans le spectre que tu nous proposes de Gamma Cassiopée, et dans le proche UV, voit-on de nombreuses raies ou des franges ? Comment expliquer la rupture de pente dans le continuum vers 3650 A ? S'agit-il d'une absorption ?
Bien à toi,
Michel Verlinden
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Re: 3D printed UVEX spectrograph

Postby Peter Somogyi » Thu Jun 22, 2017 12:31 pm

Hello Christian,

Congratulations for the stunning results!
Couple of questions:
- do you know how much of the UV light the cilindrical lens taking off? How much the fused silica / quartz lens could improve?
- what's causing the limit at 3200A ?
- what F-ratio is optimal?
- do you plan adding any connection facility attaching an Alpy guide module? (I can see you're using external guide scope)
note: Newtonian scopes are easy to modify to move out the backfocus (e.g. cut from the tube + enlarge sec.mirror; rather easy mod), if it's needed for a guide mod.
And, like the others, of course interested where did you get the optical elements from and what are their specs...

Cheers,
Peter
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