Telescope Resolution Calculator Formula
Understand the math behind the telescope resolution calculator. Each variable explained with a worked example.
Formulas Used
Dawes Limit
dawes_limit = 116 / apertureRayleigh Limit
rayleigh_limit = 138 / apertureVariables
| Variable | Description | Default |
|---|---|---|
aperture | Aperture Diameter(mm) | 200 |
How It Works
Telescope Angular Resolution
Dawes Limit (empirical, for equal-brightness stars)
theta = 116 / D arcseconds (D in mm)
Rayleigh Criterion (diffraction-limited at 550 nm)
theta = 138 / D arcseconds
Smaller is better. A 200 mm telescope resolves about 0.58 arcsec. Atmospheric seeing typically limits ground-based resolution to about 1-2 arcsec.
Worked Example
A 200 mm (8-inch) telescope.
aperture = 200
- 01Dawes: 116 / 200 = 0.58 arcsec
- 02Rayleigh: 138 / 200 = 0.69 arcsec
- 03This can split double stars separated by 0.6 arcsec on a steady night.
Frequently Asked Questions
What limits resolution in practice?
Atmospheric seeing (turbulence) typically limits ground resolution to 1-2 arcsec, regardless of telescope size. Adaptive optics or space telescopes overcome this.
What is the Hubble Space Telescope's resolution?
About 0.05 arcsec, thanks to its 2.4 m aperture and no atmospheric blurring.
Does magnification improve resolution?
No. Resolution is set by aperture. Magnification just makes the resolved detail easier to see, up to a point.
Ready to run the numbers?
Open Telescope Resolution Calculator