Pepsios Purely Interferometric High-Resolution Scanning Spectrometer II Theory of Spacer Ratios*

For the selection of spacer ratios for the Pepsios spectrometer, a theory has been developed which evaluates the parasitic light by complex integration. The problem of finding the optimum set of ratios for a given set of parameters has not been solved, but for a three-etalon Pepsios instrument operating at a resolving power of the order of 105 to 106 over a wide range of values of finesse and filter half-intensity width, a set of spacings in the ratios 1.0000:0.8831:0.7244 has been found to exhibit an instrumental transmittance with especially high spectral purity.