Speckle masking is a speckle imaging

Speckle imaging

Speckle imaging describes a range of high-resolution astronomical imaging techniques based either on the shift-and-add method or on speckle interferometry methods...

 method which involves estimation of the bispectrum or closure phase

Closure phase

The closure phase is an observable quantity in imaging astronomical interferometry, which allowed the use of interferometry with very long baselines. It forms the basis of the self-calibration approach to interferometric imaging...

s from each of the short exposures. The "average bispectrum" can then be calculated and then inverted to obtain an image. With a normal telescope aperture, a large number of short exposures must be averaged to remove the effects of the atmosphere. If a non-redundant aperture mask

Aperture masking interferometry

Aperture Masking Interferometry is a form of speckle interferometry, allowing diffraction limited imaging from ground-based telescopes. This technique allows ground based telescopes to reach the maximum possible resolution, allowing ground-based telescopes with large diameters to produce far...

 is used the bispectrum can be calculated without any noise contribution from the atmosphere (but still with a photon-shot noise error contribution). In this arrangement a ground-based telescope aperture is blocked by astronomers apart from a few holes which allow light through, creating a small optical interferometer

Astronomical interferometer

An astronomical interferometer is an array of telescopes or mirror segments acting together to probe structures with higher resolution by means of interferometry....

 with the resolving power of a diffraction-limited telescope rather than being limited by the astronomical seeing

Astronomical seeing

Astronomical seeing refers to the blurring and twinkling of astronomical objects such as stars caused by turbulent mixing in the Earth's atmosphere varying the optical refractive index...

.