Practical works…

Here is how to obtain a spectrum of the Sun with a grating, a needle and a compact numerical camera:

Plant the needle in an unspecified support and expose it to the Sun. Place a grating (here: transmission 15mm, 1200 tr/mm) in front of the objective of the camera and seek the reflection of the Sun in the needle. A dark object well laid out - in this case an armchair - makes it possible to have a spectrum on an about black backgroung. The needle do the job of the entrance slit of the spectrograph and the absorption lines are thus visible.
The image below shows the needle enlightened on the left (zero order) and the spectrum on the right (first order). Notice that all the objects in the field also induce spectra which overlap.

Zoom on the spectrum:

And after treatment: