Rayleigh Limit
Glossary 
Rayleigh Limit 
updated: 20221015 
Rayleigh Criterion or Rayleigh Limit expresses the theoretical maximum resolving power of a telescope (or microscope) according to the formula:
R = 
λ = wavelength in nm D is the diameter of the main lens (aperture) R is the resolving power of the instrument in arcsec 
Special formula for wavelength of about 562nm: 

R = 11.6/D 
D is the diameter of the main lens (aperture) 
This is also called the Dawes' Limit. 
A telescope with an aperture of 90mm will therefor have a typical Dawes' Limit or angular resolution of 1.53" arcsec.
See: Rayleigh Criterion  Wikipedia
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