Telescope Resolving Power Calculator

Calculate a telescope's Dawes and Rayleigh resolution limits in arcseconds from its aperture diameter and the observing wavelength

Frequently Asked Questions

What is the difference between the Dawes and Rayleigh limits?

The Dawes limit is an empirical rule for splitting close double stars of equal brightness and is slightly more optimistic. The Rayleigh limit is a theoretical diffraction limit based on the Airy disk and gives a slightly larger, more conservative resolution angle.

Why does a larger aperture resolve finer detail?

Resolution is set by diffraction, which depends on the ratio of wavelength to aperture diameter. A larger aperture makes that ratio smaller, so the smallest resolvable angle shrinks and the telescope can separate closer objects.

Does atmospheric seeing limit real resolution?

Yes. Turbulence in the atmosphere usually blurs images to about one or two arcseconds, which often limits resolution before the optics do. Steady air, high altitude, and good collimation all help approach the theoretical limit.

Important Disclaimer: Estimates for informational purposes only.

This calculator provides estimates for informational purposes only. Results are based on assumptions and may not reflect actual outcomes. Consult qualified professionals in relevant fields before making important decisions based on these results.