Any reflecting telescope with classic coatings can attain a lifetime of 20 or 30 years - correct handling provided. The same accounts for our protected silver-coatings, whereas the position of a stardiagonal within the optical train does provide much better protection against environmental influences, compared to the exposed surface of a primary telescope mirror.
We do regard the benefit of the BBHS hardsilver coating to be quite noticeable, compared to the reduced spectral range offered by a dielectric coating. Please check in the Internet for statements that would verify our position. Or look for the very extensive tests on star diagonals, performed by William Paolini (see tab "Downloads".
Please read more on the properties of our star diagonals and our design philosophy here: http://www.baader-planetarium.com/en/blog/baader-bbhs-reflective-properties/
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|Optical Design||Star Diagonal Prism|
|Inner Connection (lens sided)||Thread, T-2 (M42 x 0,75)|
|Inner Connection (eyepiece sided)||Thread, M34|
|Outer Connection (eyepiece sided)||Thread, T-2 (M42 x 0,75)|
|Reflection surface||Sealed BBHS coating|
|AR-Coating||Phantom Coating® Group|
|Image Orientation||Erect image, Mirror inverted|
|Optical tube length (mm)||38,5|
|Clamping System||no clamp|
|Inner Diameter / Clear Aperture (mm)||34|