Dawes' limit
Dawes' limit is a formula to express the maximum resolving power of a microscope or telescope. It is so named after its discoverer, William Rutter Dawes , although it is also credited to Lord Rayleigh.
The formula takes different forms depending on the units.
| R = 4.56/D | D in inches, R in arcseconds |
| R = 116/D | D in millimeters, R in arcseconds |
| where | D is the diameter of the main lens (aperture) |
| R is the resolving power of the instrument |
This formula agrees with the usual at a wavelength of about 460nm, somewhat bluer than the peak sensitivity of rod cells at c. 498nm.
