Burgess Optical 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 1/10th 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 1/16th wave before coating. After
the dielectric coatings are applied, the mirror has a nominal 1/10th wave surface. That is a
1/10th 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.

Price - £75.00

The Astronomy Shop

1 Tone Hill. Wellington

Somerset TA21 0AU

United Kingdom

Telephone: +44 (0)1823 665510