Resolving Power of a Telescope

The Resolving Power of a Telescope calculator computes the angular distance between two stars on the limit of visibility for a telescope.

INSTRUCTIONS: Choose units and enter the following:

• (λ)  Wavelength of light
• (D) Diameter of Telescope

Resolving Power (α): The calculator returns the Resolving Power in  arc seconds.  

The Math / Science

The resolving power of a telescope is the angular distance between two stars that are just barely visible through the telescope as separate images. The resolving power α in arc seconds of a telescope with diameter D in meters that is collecting light of wavelength λ in nanometers equals is given by this formula.  The formula for the resolving power of a telescope is:

     `α = 2.06 x 10^5 ( λ / D )`

where:

• α = resolving power
• λ = wavelength of light
• D = diameter of telescope

Astronomy Calculators