A one hour construction spectrograph and spectra

[Christian Buil]

The miracle of a fiber optic link between the telescope and spectrograph (Shelyak interface)... yesterday I built a spectrograph in an hour of time from few photographic optics and of course a grating, and just after, observation! Spectroscopy is simple

Here an image of a R = 1300 version of improvised setup:



The outburst of Be star V442 And (potential swap between very different spectrograph take some seconds only) - two visions of the same object:



Symbiotic star CI Cyg:



A hot star:



A intermediate temperature star (sodium D1-D2 lines are just resolved):



etc, etc.

I call this process the "Instant spectroscopy" (ou comment construire un spectrographe "sur le pouce").
Ideal for pedagogic purpose for example and demos about spectroscopy.

Christian

[Andrew Smith]

One hour but multi-thousand Euro? Well done Christian, you certainly manage to produce a whole series of top class spectrographs and deliver interesting spectra.

Regards Andrew

[Miguel Rodriguez]

A very good resolution, R=1300, for a quick setup. The idea is very attractive.

[Christian Buil]

The key of Instant Spectroscopy is the optical fiber interface, and you are right Andrew, thousand euros are necessary. But after... you are free for all. You can for example make a very low cot spectrograph with a StarAnalyser and two old oculars, up to a super high resolution setup.

Ideal for education and for experimenters (my use of a true optical banch is only a detail here for example, wood structure is possible,... by also now use 3D impression for a quick and playfull construction). I believe that the initial investment can be quickly "payed".

Christian

[Andrew Smith]

The key of Instant Spectroscopy is the optical fiber interface, and you are right Andrew, thousand euros are necessary. But after... you are free for all. You can for example make a very low cot spectrograph with a StarAnalyser and two old oculars, up to a super high resolution setup.

Ideal for education and for experimenters (my use of a true optical banch is only a detail here for example, wood structure is possible,... by also now use 3D impression for a quick and playfull construction). I believe that the initial investment can be quickly "payed".

Christian

I fully agree. I have been working on an optical fiber interface similar to yours but have got distracted by automation. Your work encourages me to start again.

Regards Andrew

[Christian Buil]

A comment. The major difficulty concern probably the photographic lens qualities. Excellent for the visible spectral domain, but failing, because chromatism aberration, in the blue and of course UV. For Shelyak product line we develop specific optics for spectroscopy. The situation is not so perfect for setup done by yourself.

But mirror and apochromatic lens (see VHIRES example) are possible for some functions, and ... visible part of the spectrum cover a large domain of astrophysics!

Best regards

Christian

[Robin Leadbeater]

Good fun!

Here is another "junk box" spectrograph.
http://www.threehillsobservatory.co.uk/ ... opy_19.htm
Less than an hour to build but more than that to find the right components in the junk box

Robin

[Robin Leadbeater]

It also reminds me of Mario Maessen's "extreme spectroscopy" splitting of the Na D lines using a Star Analyser 100
https://groups.yahoo.com/neo/groups/sta ... opics/2473

Robin

[Christian Buil]

Of course, a key piece of my setup is the fiber optics interface at the telescope level (Shelyak Instruments model):



A side effect is the presence of only one fiber for the moment. During observation
of a faint star, we capture also the sky background is the same data. From my
observatory, very highly polluted by city light, specific sky subtraction is necessary
for faint objects. Here a demo of the procedure for star HD228860 (V=9.72, only 1200 seconds
exposure... fiber link can be relatively efficient):



The "sky" spectrum is a "reference" (not taken systematically for each stellar spectrum).
HD228860 is a BeSS star objet (Be star). At the second stage, the analysis show the correction of interstellar
extinction (a specific tool is into ISIS).

Christian

[Robin Leadbeater]

Hi Christian,

The need for a separate sky exposure has put me off low resolution fibre fed spectrographs for faint objects, particularly when sky conditions can change so quickly. Do you think there could be value in designing a fibre feed with a separate fibre for the sky so that both star and sky could be recorded in the same exposure ? (difficult for an echelle perhaps where the sky fibre spectrum would need to fit in the gap between the orders but ok for a low resolution faint object setup)

Cheers
Robin