spider diffraction

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.
References in periodicals archive ?
The high-resolution R-AXIS SPIDER diffraction system combines components needed for a high performance small molecule crystallography system.
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.
The effect of spider diffraction can also be expressed roughly as follows: