= Transit dilution
{title2=$\delta_{\rm obs}=\delta_{\rm host}/(1+D)$}
Constant extra light makes an <exoplanet transit> appear shallower. If the host <star> supplies out-of-transit <observed radiative flux> $F_\star$ and an unresolved source supplies $F_c$, let $D=F_c/F_\star$. Then $\delta_{\rm obs}=\delta_{\rm host}/(1+D)$. For $D=1$, a true <exoplanet transit depth> of $0.010$ appears as $0.005$; ignoring <transit dilution> gives a <radius> ratio $\sqrt{0.005}\simeq0.07071$ instead of $0.10$, under the same uniform-disc assumptions.
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