This is the same Star Diagonal TeleVue builds for their diffraction limited telescopes. This package also includes a TeleVue HiHat 2" to 1.25" Adapter (Part ASF-8125) so you can use your fine 1.25" eyepieces as well. Exquisitely crafted to fold the light beam exactly 90°. The mirror blank of the TeleVue 90 Degree Enhanced 2-inch Star Diagonal is polished to 1/10th the wavelength of light and vacuum coated with enhanced aluminum. Then it is overcoated to protect the delicate mirrored surface.
To ensure the optical alignment of the TeleVue 90° Enhanced 2" Star Diagonal, the body is CNC machined from one solid block of aluminum. For maximum contrast they cut anti-reflection threads into the inner surfaces.
If you've ever had the experience of fumbling in the dark while moving your filter from one eyepiece to another, you will especially appreciate the convenience of the 48 mm filter threads cut into the body of the TeleVue 90° Enhanced 2" Star Diagonal. You can use only one 48 mm filter in your diagonal and then change out your eyepieces at will, without bothering to swap filters! A captive eyepiece lock-screw adds the finishing touch.