Most accurate way to guide – improved accuracy compared to using a separate guide scope 12.5mm multi-coated prism with aluminized backing for maximum reflectivity and illumination to the autoguider Fixed-orientation helical focuser for easy, smooth and accurate autoguider focus 48mm clear aperture supports full frame cameras without vignetting Includes adapters with the correct spacing for DSLR cameras, Nightscape CCD and other popular astroimaging cameras Ideal for Schmidt- Cassegrain and EdgeHD telescopes