Secondary spectral standards based on Fabry-Perot etalon

We discuss the possibility of using a Fabry-Perot interferometer as a source of the comparison spectrum for calibrating the wavelengths in the spectra of astronomical objects. For low dispersion, a Fabry-Perot etalon has been made in the form of a three-layer structure by sputtering a glass substrate in vacuum in the following order: firstly, a thin translucent layer of aluminum, then a layer of several micronthick glass, and another layer of semitransparent aluminum. For high dispersion, a Fabry-Perot etalon has been made of mica several tens of microns thick, the surface of which was sputtered with translucent coatings of aluminum. In the second case, the density of transmission peaks is higher than the density of intense spectral lines of thorium by a few dozen times.