Enhance a home build spectrometer

The resulting images from this spectrometer are promising.

A first starting point might to use something better than a cereal box. Preferably a box which is completely black inside, this improves the contrast of the image.

A second step could be to replace the CD by a diffraction grating and a mirror which are both not curved, the input slit could be replaced by something, where you can vary the distance with screws.

For any kind of 'real' science you might want to measure the output spectra. So instead of projecting it onto the nearest surface a fixed paper screen might be nice, where you can draw a scale for the individual wavelengths, e.g. to identify different elements (e.g., Na-lamps at night, fluorescent light bulbs).