wpo - simple grism spectrograph with reflective slit

 
Another simple arrangement for a low resolution spectrograph using

1] a chrome eyepiece as a reflective slit

2] an achromatic doublet lens of ~120mm fl as a collimator eg parallel light

3] a combined transmission grating in contact with a weak prism eg a grism

4] a camera focused on infinity to record the spectrum.

The Mercury [Hg] lamp is a common fluorescent tube showing emission lines whilst the remaining spectra of sunlight with magnesium [Mg] and sodium [Na] identified.