Jm. Beckers, ON THE EFFECT OF NARROW-BAND-FILTERS ON THE DIFFRACTION-LIMITED RESOLUTION OF ASTRONOMICAL TELESCOPES, Astronomy & Astrophysics. Supplement series, 129(1), 1998, pp. 191-194
Sometimes Fabry-Perot and other narrow band filters are used for astro
nomical imaging in the so-called telecentric mode. In it the pupil is
collimated through the filter, resulting in different incidence angles
on the filter for rays coming from different parts of the objective.
This results in variations of the central transmission wavelength, whi
ch broaden the effective filter bandpath. In addition each wavelength
within this filter bandpath sees a different illumination of the pupil
when viewed from behind the filter. This causes the diffraction limit
ed point-spread-function to vary with wavelength. With the advent of d
iffraction limited imaging using adaptive optics, this can cause compl
ications. In this note I examine the magnitude of this effect.