= Visibility of a one-dimensional uniform source
{title2=$V/V(0)=\operatorname{sinc}(\pi b_p\Delta\alpha/\lambda)$}
A centred uniform source of angular width $\Delta\alpha$ has normalized visibility $V/V(0)=\operatorname{sinc}(\pi b_p\Delta\alpha/\lambda)$, with $b_p$ the projected baseline along that angular coordinate and $\operatorname{sinc}x=\sin x/x$. The result is the integral of the point-source complex phase over source brightness. Its first null occurs at width $\lambda/|b_p|$; negative values are phase reversals rather than negative brightness.
Back to article page
