... by¹

In Equations 4, 5, 6 and 7, a generic area $A$ must be used instead of $\pi\,D^2/4$ for non-circular telescopes.

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... yield²

Note, however, that in order to obtain the overall flux usable for scientific studies the spectrum of the source must be weighted by the transmittance of the optical telescope asembly (OTA) and by the detector quantum efficiency (DQE).

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