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Marie Curie Intra-European fellow of the European Commission.

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... value

The residual intensity outside the solar disc, caused by stray-light, is often called aureole.

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... ratio

The Strehl (intensity) ratio is defined as the ratio between the central peak values of a PSF and the one of an ideal, i.e., aberration-free, diffraction-limited PSF. It provides a measure for the deviation from the diffraction limit.

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... telescope

It should not be confused with the Rayleigh criterion, which is defined with an additional factor of 1.22 for the position of the first minimum surrounding the central Airy disc (approximately the first minimum of the Bessel function of the first kind).

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