Angular resolution (by a single telescope)
Point-like sources separated by an angle smaller than the angular resolution cannot be resolved. A single optical telescope may have an angular resolution less than one arcsecond, but astronomical seeing and other atmospheric effects make attaining this very hard.
The angular resolution R of a telescope can usually be approximated by this formula.
For example, in the case of yellow light with a wavelength of 580 nm, for a resolution of 0.1 arc second, we need D = 1.2 m.
This formula, for light with a wavelength of about 562 nm, is also called the Dawes’ limit.Related formulas
|R||Angular resolution R of a telescope [rad] (dimensionless)|
|λ||Wavelength of the observed radiation (m)|
|D||Diameter of the telescope's objective. (m)|