# Telescope Field of View/Resolution

## 1 Resolution

The angular resolution of a diffraction-limited telescope is,

$\theta = 1.220\frac{\lambda }{D} \approx \frac{\lambda }{D}, \,\!$

where 1.220 is a factor introduced by the use of a circular aperture.When we work in the radio regime of the spectrum, we do not have to worry about the atmosphere itself inducing phase shifts in our signal, so we operate at this diffraction limit. The long wavelengths involved in radio, however, do cause us a problem in that we require large telescopes to get down to the same angular resolution of a much smaller optical telescope operating at the diffraction limit (add to that that our signals tend to be pretty weak as well, which means we need a large collecting surface). As you are well aware of by now, using an interferometer helps us with our resolution difficulties, because by combining the signals collected from telescopes separated by some baseline B, we are able to achieve an angular resolution,

$\theta \approx \frac{\lambda }{B} \,\!$