spider diffraction

The characteristic spikes of light in the form of a cross seen in the image formed by a Newtonian reflector. They result from diffraction effects caused by the diagonal supports – the spider – and are additional to the diffraction from the circular edge of an objective lens or a mirror, which converts a star image from a point to an Airy disk in refractors and reflectors.

Collins Dictionary of Astronomy © Market House Books Ltd, 2006

References in periodicals archive

What about spider diffraction? Spherical aberration?

Treasures from the archives: thar's gold in them thar back issues

Everything from the effects of a central obstruction to surface roughness on the mirrors to spider diffraction to scatter in the reflective coatings has been suggested as a possible explanation, but when these are analyzed thoroughly they don't fully account for the Newtonian's temperamental behavior.

Improving the thermal properties of Newtonian reflectors - part 1

Although the emphasis throughout the volume is on geometrical analysis, principally with spot diagrams, Wilson does not shirk from explaining why diffraction effects are important and how they (including spider diffraction) may be appraised.

All Things Reflecting

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