An refracting telescope objective is used at to observe a double star of angular…
PHYSICS · Subjective · Fermi University Physics · Optics & Photonics · Interference and diffraction · Interference and diffraction
Optics and Photonics, Ch Fraunhofer diffraction from apertures and gratings
Problem
An 80mm refracting telescope objective is used at λ=500nm to observe a double star of angular separation 1.5′′. With a 20× eyepiece the pair appears as one blurred image. The observer increases the eyepiece power to 40×, arguing that doubling the magnification will reveal the two stars separately. Evaluate this claim, giving the telescope's Rayleigh resolving angle in arcseconds.