A system for correcting infrared (IR) radiances includes an imager for receiving IR radiances and outputting intensity data corresponding to pixels in the imager. Also included is a stray light estimator for receiving the intensity data and estimating stray light in the intensity data. The stray light estimator includes a Bessel filter for low pass filtering the estimated stray light and providing corrected intensity data as an output to a user. The Bessel filter is an n-pole recursive digital filter, which is expressed as a ratio between (a) an (n−1) order polynomial of a complex number and (b) an n order polynomial of a complex number, where n is a positive integer. The Bessel filter includes an infinite response curve, in which the response curve monotonically decreases in amplitude as a function of frequency per pixels.