The spectral resolution obtained using TAURUS is equal to the free spectral
range of the etalon divided by its finesse. The free spectral range is
a function of the etalon gap and the wavelength, and is summarised for the
etalons currently available in Table .
The etalon finesse depends on a number of factors, including the surface
quality and reflectivity of the etalon plates, and the accuracy with which
they can be maintained in alignment. Values of the finesse measured on the
telescope are typically about 20, and the spectral resolution obtained
with this finesse for each of the TAURUS is etalons is given in Table
.