A spectrograph particularly suited for work in hyperfine structure is discussed. It consists of a Fabry-Perot etalon and prism spectrograph built as a single unit to eliminate many of the errors introduced when the apparatus is assembled in the usual way.
L. P. GRANATH and R. K. STRANATHAN, "A Hyperfine Structure Spectrograph," J. Opt. Soc. Am. 26, 279-279 (1936)