Prism diagonals give less scatter and therefore better contrast than diagonals using reflective mirror surfaces, including dielectric ones.
Prism diagonals are therefore especially good for high power planetary and lunar observing where sharpness and contrast are critical, especially with high quality refractors with an F7 or longer focal ratio.
Regardless of the coating method used, all reflecting mirrors consist of tiny particles evaporated onto glass which, no matter how carefully reposited, will produce scatter and reduce contrast.
The Altair prism diagonal has a BK7/K9 prism with excellent clarity and smoothness, as well as special anti reflective coatings.
The prism surface cannot even be seen with the naked eye when looking into the diagonal, unless there is dust on the surface.
- The special "Positive Lock" compression ring will never mar your accessories and is completely secure.
- Ideal for refractors and large eyepieces or binoviewers.
- Top quality prism with special broadband multi-coatings.
- Clear aperture of 43mm, with an optical path distance of 125mm.
- Essentially maintenance free.
- Includes a 2" to 1.25" adapter with brass compression ring for smaller 1.25" eyepieces or GPCAM/Hypercam.
- Threaded for use with standard 2" astro filters (M48x0.75mm thread).
- Blackened interior for high contrast (especially recommended for the moon, sun and planets!).
- Includes dust caps both ends.