Astrophysics (index)

Airy Disk

(Airy Disc, Airy Pattern)
(image pattern an optical system produces from light from a point)

The Airy Disk (or Airy Disc or Airy Pattern) is a pattern of light within a telescope image produced by light from a point source, the general case for stars. The pattern is specially an Airy Disk if the telescope has a circular Aperture. The Airy Disk pattern is a round spot surrounded by concentric circles. This is a Diffraction pattern due to the aperture size and shape of the telescope: the larger the telescope, the smaller the Airy disks that it produces, and is a limiting factor in a telescope's Angular Resolution. A telescope that solves all the other problems that affect angular resolution (e.g., incorporating an Adaptive Optics (AO) system) is described as Diffraction Limited.

The Airy Disk's first minimum (ring with less light) is at approximately:

sin θ ≈ —
  • λ - Wavelength
  • d - diameter of the aperture
  • θ - angle "across the sky", i.e., if another light source was that angle away from the first, then it would be at this ring.


Referenced by:
Angular Resolution
Antenna Pattern
Aperture Photometry
Point-Spread Function (PSF)
PSF Fitting
Speckle Suppression
Strehl Ratio