Optional holographic attachments screw into the laser aperture and have a white screen front surface. They contain an optical element that diffracts most of the laser light into a diverging symmetrical pattern around the central beam. The projected pattern is useful for centering optical elements by making it symmetrical with the edge of the optic.
Three different patterns are available:
- A 10 x 10 line square grid pattern is supplied as standard unless otherwise requested because it is the widest pattern. It spreads 21 degrees which allows centering of optics as fast as f/ 2.7. This pattern is recommended for general use because it can be used with the fastest telescopes likely to be encountered.
- A nine-concentric circle pattern is available that spans 10 degrees and will reach to the edge of f/ 5.7 optics. This pattern is recommended for scopes around this focal ratio or slower. Because the laser light is spread over a smaller area it is brighter than the square grid pattern, and this makes it particularly useful with Cassegrain scopes, where the pattern impact is sometimes scrutinized on the mirror surfaces. The projected pattern is seen only by light that is scattered from dust, dirt, or optical roughness, so a brighter pattern is better, especially if the mirrors are very clean.
- A cross-hair and circle “scope” pattern is available that spans 10 degrees. It has utility for non-Barlowed , conventional Newtonian primary collimation, where the primary is adjusted to return the reflected central laser beam back into the laser aperture of the collimator. The cross-hair intersection makes it easier to see when the return beam is centered on the collimator face.
