I wish to create a spectra scope, to analyze some of my lights, however I'm not shoveling out 2200 or 1500 dollars for a nice one. And I'd rather do something a bit better quality than a CD spectra scope. I'm thinking of using a diffraction grating from EdmundOptics with 1800 Grooves per millimeter. I want to protect the grating with a glass lens (if it won't interfere with the spectra. Instead of cardboard I want to use plastic. It is alot cleaner than paper which emits particles. I'm thinking the whole device will be square in shape. My primary issue is I want to get the thinnest opening possible on the light receiving end. It is my understanding that the thinner the opening the higher the resolution? How would I achieve this?  Is there super thin premade lenses for this purpose?

https://www.edmundoptics.com/p/1800-grooves-25mm-square-240nm-ruled-diffraction-grating/19117/

I'm thinking of getting either the 25x25mm square unit or the 12.5x12.5mm unit. It is a debate between cost and ease of working with. 12.5mm square grating would be pretty tedious to work with.

Given the price of that grating you're considering, I think you'd be better off buying a complete spectroscope on e-bay.

My issue with ebay is that it's full of either antique spectroscopes that I question the accuracy of, given that alot of them utilized prisms, or cheap looking things that look like they might not give a a great resolution.  I want to view both strong Spectral lines and weaker ones. With a purchased grating I know what I'm getting and I can build around it. Not a huge fan of the price but I will be shopping around to see if there is cheaper ones at the same quality.

What accuracy do you want when it comes to a visual inspection of the spectrum? Using this or that grating won't have any impact on how the eye perceives light, only on how well separated the discrete lines will be perceived. But again, what resolution are you seeking exactly?

Besides, spectroscopes with the double Amici prism are brighter than those based on gratings since light is not dispersed in different diffracted orders. I use one spectroscope of the former type, which you can find on e-bay for around 100-200 USD, and I can distinguish the two D-lines of sodium (0.597 nm apart) clearly, which should be more than enough for your needs. If you need more than that, then be ready to shell out some serious money.

Enough resolution to distinguish the two bands coming from a SOX lamp is definitely plenty for me. What spectrometer do you have?

I guess I was misguided on the prism vs diffraction grating.  I read that diffraction gratings were better.

I too am interested in getting or building some sorta spectroscope. I have thought about doing the DVD thing as an experiment, Even had some stuff set aside for it...but never ended up doing anything. .lol. (the thought of diffraction grating also has crossed my mind.)

I read that diffraction gratings were better.

That really depends on the application and on the required characteristics of the instrument. For spectrometers, gratings are indeed better suited due to the linearity of their dispersion and the fact that spectral resolution and optical efficiency can be easily tailored via the shape and spacial frequency of their surface features. But for handheld spectroscopes, where requirements are different, the double amici prism provides better overall results for a lower cost.

The device I use to quickly check the content of discharge lamps is a standard double amici prism spectroscope with wavelength scale from Wollensak, you can find equivalents on e-bay.