Enjoy better views through your telescope and change eyepieces and accessories faster and more easily with the Celestron 90° Dielectric Star Diagonal. The diagonal has a 2" holder for today's larger accessories and imaging gear, and it comes with a 1.25" reducer adapter to make it compatible with the most popular size of gear from eyepieces to Barlows, filters, and a near-infinite array of accessories.
Designed with diffraction-limiting optics, its BK7 mirror is treated with 58 layers of dielectric coatings that produce a reflective surface greater than 99% so more incoming light makes it to your eye—this is especially important when viewing dim deep-sky objects where every photon of light is important.
For the eyepiece holder side of the diagonal, Celestron eschews convention and replaces the ubiquitous three thumbscrews to tighten the interior compression ring with a twist-lock. Utilizing a twist-lock not only makes swapping your eyepieces and accessories faster and easier, it properly centers the eyepiece and maintains proper optical alignment. This version of the Dielectric Star Diagonal comes with two adapters for the telescope side: A 2" nosepiece that fits into standard drawtubes and a threaded ring that fits standard Schmidt-Cassegrain telescope (SCT) visual backs. Using the SCT adapter provides a solid and secure connection while limiting additional optical distance, which is important for imagers performing eyepiece projection techniques. The aluminum housing has a black anodized finish, and the interior is painted flat black with blackened threads to reduce reflections.