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Accessories: 2" Dielectric Diagonal

The Burgess Optical 2" diagonal with dielectric coatings is a premium diagonal suited for use with any refractor telescope. The Dielectric Diagonal has 99% reflectivity and a surface accuracy of 1/10^th wave! This version of the 2" diagonal has a body with a glossy finish.

With mirrors, the most important characteristic is the surface accuracy with reflectivity coming in second. Rayleigh's Criteria is that the total wavefront error should not exceed 1/4 wave peak-to-valley to avoid optical degradation. The mirror in the Dielectric Diagonal is low thermal-expansion glass that is polished to approximately 1/16^th wave before coating. After the dielectric coatings are applied, the mirror has a nominal 1/10^th wave surface. That is a 1/10^th wave variation across the full surface - edge to edge - not just the center of the mirror. In addition to the ultra-flat mirror surface, the mirrors have 99% reflectivity.

The Dielectric Diagonal includes a zero-height 1-1/4" adapter. Both the diagonal and the adapter have a compression ring clamping mechanism.

The Dielectric Diagonal has these features:

• The mirror is thick glass and has a dielectric coating.
• The mirror has 1/10th wave accuracy - after being dielectric coated!
• The mirror has 99% reflectivity!
• The diagonal and the 1-1/4" adapter have brass compression rings to prevent marring of your eyepieces.
• The 1-1/4" adapter is recessed so your 1-1/4" eyepieces require less focuser in-travel.
• The barrel has a safety wedge to prevent the diagonal (and eyepiece) from falling out of the telescope if the telescope retaining screw loosens.

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