Back in 2003 I designed and built a grating based spectrograph primarily used for casual solar spectral studies as well as gaining an appreciation of the beauty and elegance of it’s spectral lines.
This served reasonably well for many years of on and off again operation, but always had a few niggles I never quite worked out. The grating turret was a bit wonky and would sometimes get hung up. Additionally it would slightly wobble during rotation causing a shift in spectrum placement on the camera sensor or viewing eyepiece
Another source of occasional frustration was the adjusting mechanism on the entrance slit which did work…just not very well. The final aspect was it’s rather cumbersome size for it’s purpose…With those things in mind I’m endeavoring to reduce it’s overall dimensions, simplify the problem areas and create a friendlier instrument in practice.
To begin I’ve looked at a rather simple arrangement which offers somewhat less flexibility (in my own implementation) but in return gains solidity, portability and simplification of operation (at least, that’s my wish).
Here’s my proposed layout diagram based on a German spectroscopy forum’s Minispec design by author Danial Sablowski:
And here’s a few pieces and parts I’ve got at this point… First a pair of cheap Walmart Pencil sharpeners I purchased for a whopping 47 cents each:
And the parts we need from the sharpeners (blades for our entrance slit)
And the completed (for the most part) spectrograph slit assembly:
Next in order, to properly determine optimal part configuration, I found a suitable cardboard box of roughly similar dimensions to act as a flexible test bed to this end. As shown, I placed the entrance slit assembly and 35mm collimator lens to better gage focal length adjustments. The slit assembly tube(s) allow two points of adjustability, which were set at midway.The collimator lens was set roughly at its correct focal length. A small hole was cut out in line with the slit/collimator positioning to permit a finder scope, set at infinity focus, in order to make the necessary adjustments to bring the slit into sharp focus. Those readings were jotted down in my project notebook.
The final enclosure will also have a 20mm hole bored to ensure the collimator lens has good focus on the slit jaws.
That’s the story so far…back when I’ve further progress to report…..Thanks for looking
“To invent, you need a good imagination and a pile of junk.”
-Thomas A. Edison