The Littrow Spectrograph
The Littrow design is very popular, only requiring a single achromat as a collimator/ imaging lens. More suited to higher f ratios (>f8) but can provide a reasonably compact assembly and high (R=10000) resolution. The Shelyak LHiresIII is a good example of this design.
(The Littrow design was developed into the original Spectra-L200 instrument, which unfortunately is currently unavailable. It used 150/ 300/ 600/ 1200 or 1800 l/mm gratings. Maximum resolution R=9000)
This article The Littrow Spectrograph gives details of the original L200 prototype build.
HIRSS Fulvio Mete's high resolution version of the Littrow.