  This paper presents a method for determination of interference filter
parameters such as the effective refraction index and the maximal transmittance
wavelength on the basis of image processing of a spectrogram produced by
Spectrometer Airglow Temperature Imager instrument by means of data processing.
The method employs the radial sections for determination of points from the
crests and valleys in the spectrograms. These points are involved in the least
square method for determination of the centres and radii of the crests and
valleys. The use of the image radial sections allows to determine the maximal
number of crests and valleys in the spectrogram. The application of the least
square fitting leads to determination of the image centers and radii of the
crests and valleys with precision higher than one pixel. The nocturnal course
of the filter parameters produced by this method is presented and compared with
that of the known ones. The values of the filter parameters thus obtained are
closer to the laboratory measured ones.
