Analytical description of a Fabry-Perot spectrometer. 5: Optimization for minimum uncertainties in the determination of Doppler widths and shifts.

Based on the statistical criterion of least uncertainty, it has been found that there exists an optimum combination of source and instrumental parameters, which lead to the most efficient use of a Fabry-Perot spectrometer in the measurement and determination of either line profile position or temperature. Results are given in order to optimize the design of a spectrometer and/or quantitatively deduce the uncertainties of determination from measurements. Comparisons between the present results, the luminosity-resolution product method, and the usual method to determine line positions show the present quantitative method to give the most efficient spectrometer and the best estimates of uncertainty. A useful result of this investigation shows that a low reflective finesse etalon provides the optimum spectrometer. The implicit relaxation of the surface quality of the flats and precision of etalon adjustment deduced from this result lead not only to simplified operation but to lower instrumental costs as well.