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`\alpha = 2.06 \times 10^5 ( \lambda / D )`

0.3777

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 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