Hi , ELPS .
I have an old 2 inch mirror diagonal from the 1980's ( Celestron ) , a no name 2 inch 96% dielectric from the 90's ( not bad ) and 2 , GSO 99% dielectric Quartz from now ( 2012) .
Using all my refractors, I enjoy trying a comparism between these 3 and mate the new Dielectric Quartz diagonals are the way to go
, in all ways the view is better .
The 1/16th wave might have something to do with this , but the brightness, sharpness and colour rendition are all far superior .
. in the new Dielectric Quartz diagonals .
In my eye they are worth investing in .
Oh yea , the dielectric reflective couting is guarenteed for 25 years , if left alone . Thats way more than any over coated aliminium coating .
Brian.