What I want to do
answer two questions: Can straylight be eliminated in a simple spectrometer setup through using a double slit? Can a double slit reduce the length of the spectrometer?
My attempt and results
I took the block that comes with the desktop spectrometry kit and cut two grooves in it cross-wise.
Questions and next steps
Waving it around there is definitely no stray light and it gives a clear spectrum. The .18mm slits are a little small for capturing much light from fluorescence spectra. I'm going to trade them out for some laser cut slits tomorrow and try again.
Why I'm interested
it would be easier to mount a spectrometer on a smartphone and other devices if it were smaller and more rigid.