Where did you buy the black piece that holds the spectroscope (its rectangular with a hole the right size for the spectroscope and with what looks like a brass screw for holding it in place)? It doesn't show it listed in the parts on the github page.
Where did you buy the black piece that holds the spectroscope (its rectangular with a hole the right size for the spectroscope and with what looks like a brass screw for holding it in place)? It doesn't show it listed in the parts on the github page.