OR: Sun spectrum walkthrough

[Julien Lecomte]

Hello,

A while back, I posted about building a high resolution spectrograph using a 3D printer. Some of you probably thought I was kidding :) Well, here is the almost-final result:

(no guide camera, because for this exercise, I don't really need one)

It's close enough to completion that I was able to point it towards the sky and capture a few snapshots of the spectrum of the Sun ("polluted" by the Earth atmosphere of course...) and here they are. They were taken with a color camera (not the camera I'll use to capture science data, I have a monochrome camera for that, but here, for a first attempt, it's fun to see colors...) Note that I am using a 10µm slit, so my resolution is about 40,000, which equates to a little over 0.1Å in the visible spectrum. That is why you can see the two lines of the sodium so clearly, even though they are separated by only 0.6nm! I'll most definitely use this thing to carefully measure the bandpass of my narrowband filters...

1. The famous H-alpha line:

2. The H and K lines of calcium, in the near ultraviolet:

3. The triplet line of magnesium:

4. The doublet line of sodium:

5. Molecular oxygen in the Earth's atmosphere, in near infrared:

Hope you like it! This is a new universe of possibilities for me, and I cannot wait to stick that to the back of my telescope. That being said, I need to study ways to calibrate the darn thing, using neon lights. Lots of DIY solutions, it's a lot of fun.

- Julien, the token Frenchman -

[Jay Freeman]

Fantastic! And I hope to see a detailed article on the design and construction of your spectrograph somewhere, sometime, somehow.

Historians of amateur astronomical equipment might be interested in the articles about spectrohelioscopes and spectroheliographs in _Scientific_American_ in the 1930s or so, which were reprinted in Ingalls's "Amateur Telescope Making" books, I believe in volume II ... ? They were quite impressive, and if there is ever a book about steampunk scientific apparatus they should figure (*ahem*) prominently ...

My first scientific publication :-) :-) :-) was a letter to Sky and Telescope magazine that I wrote when I was in Junior High School or High School -- that would be 1958 to 1964 -- describing observations of the solar spectrum that I made with a simple diffraction-grating-and-slit spectroscope from Edmund Scientific: Since the sun had plenty of light, I was able to narrow the slit to well under 1 mm, which was adequate to show most of the major lines in the visible part of the spectrum.

-- Jay Reynolds Freeman
---------------------
Jay_Reynol...@mac.com
http://JayReynoldsFreeman.com (personal web site)

On Jul 1, 2022, at 17:12, Julien Lecomte <julien....@gmail.com> wrote:

Hello,

A while back, I posted about building a high resolution spectrograph using a 3D printer. Some of you probably thought I was kidding :) Well, here is the almost-final result:

[...]

[Julien Lecomte]

Hi Jay,

The spectrograph is not my design. For more information, see 

http://www.astrosurf.com/solex/sol-ex-presentation-en.html

The photograph I included in my post shows the Star’Ex configuration, which includes a system to guide during long exposures.

- Julien

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[Rahul S]

This is absolutely fantastic Julien! Thanks for sharing, and looking forward more updates and pictures! 

[Rajah]

Fantabulastic!!!!

I see new material for a SJAA tech talk. It would be great to hear about build details and more about science behind your choices, esp with a live QnA session.

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[Akarsh Simha]

This is absolutely fantastic! I recently got hooked after we looked visually at the spectra of a couple stars and the Cat's Eye Nebula at GSSP through Alan Agrawal's 24" telescope with a Rob Brown "Spectre" spectroscope belonging to Howard Banich. I would love to see your results with other stars and stuff. There is a huge amount of educative science that can be done here.

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[Pawan Singh]

Julien

I have been reading the Starex and Solex pages after your post on the TAC. I was wondering if you can answer these questions:

1. Does the kit on Shelyak site build one Solex and one Starex kit or one can build either one of them using the stuff they provide?

2. If one does not have a 3-d printer, are there commercial 3d-printer stores where one can go and print the parts based on files provided on Solex site?

Thanks

Pawan

[Julien Lecomte]

Hello Pawan,

1. The kit allows you to build a Star’Ex, which is a superset of Sol’Ex. That being said, switching from one configuration to the other is very time consuming, so some people build both, which therefore requires 2 kits.

2. In France, it is possible thanks to a company (Azur 3D print iirc) owned by an amateur astronomer. Here, in the US, forget about it. It requires doing the 3D printing yourself. And contrary to what the web site implies, it is NOT an easy project to print, not at all! But with some patience, it is doable.

- Julien

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[Pawan Singh]

Thanks Julien.

Pawan

[Kurt Kuhlmann]

You can get very reasonable 3D prints from here.  We often use them when we need stronger parts like PA12 Nylon

https://jlcpcb.com/3d-printing

 

 

Kurt

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[Jonathan Lawton]

Hi Julien!

This is really cool!  I'm tempted to order a kit right away but am trying to do my homework first so I know what I'm doing. :)

Is there a reason the Star'Ex configuration could not be used for solar imaging?  The difference is the addition of the guide port, right?  Couldn't this just be covered?

I'm reasonably proficient with 3D printing so I'm sure I can make and assemble the parts.  Aside from printing challenges, is this really as plug and play as it seems?  How much fiddling around did it take to get your first spectrum of an interesting target?

The folks at Shelyak say the kit is being split into 4:

1) A Sol'Ex only kit

2) A Star'Ex / Sol'Ex kit, the same as the current offering but including "There is also the multi-slit inside which allows you to switch from a telescope to a telescope." (I don't understand this, I assume they mean multiple slits to work with longer focal length telescopes?)

3) A low res Star'Ex "with new doublets" (visual)

4) A low res Star'Ex (as far as UV)

Any thoughts on why one would choose the low res Star'Ex versions?

Jonathan

[Julien Lecomte]

Hi Jonathan,

I’ll reply off list later today.

- Julien

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