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Stargazing Aug 31st ✦ 7pm-10pm
Stargazing Aug 31st ✦ 7pm-10pm

MAXBRIGHT 2" Mirror Diagonal with Dialectric Coating and Brass Locking Ring


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The Astro-Physics 2" MaxBright Diagonal was designed with several unique features to provide optimum performance and years of use.

Dielectric Coatings
The Astro-Physics 2" diagonal has a very high-tech dielectric coating that was developed originally for military optics used in hostile environments such as blowing desert sand. There is no aluminum or other reflective metal used. The reflective surface consists of multiple layers of thin film oxides, similar to those used in anti-reflection coatings. The coatings are deposited using a sophisticated low-stress deposition method.

Advantages of the Astro-Physics Dielectric Coatings
Reflectivity - Reflectivity is above 99% over the entire 4000 to 7000 Å photo-visual range. Thin film coatings have extremely low surface scatter compared to aluminum or enhanced aluminum coatings. Dielectric coatings (if done right) will result in less scattered light. Examination with a laser source shows approximately a 5 fold reduction in surface scatter, a tremendous improvement over aluminum mirrors.

Durability - The main advantage of a dielectric mirror coating (again, if done properly) is that the surface will be durable and will last for a lifetime. It will never tarnish and will be resistant to sleeks when cleaned. This means that for critical planetary viewing you can clean the surface and not have to worry about creating microscopic sleeks which lead to scattered light and lower contrast.

For critical planetary viewing it is important to have the eyepiece and diagonal surfaces as clean as possible. You will find that even after one observing session the diagonal surface will accumulate crud. The inherently high contrast and cleanability of the Maxbright insures that it is never a limiting factor when viewing subtle planetary detail. For cleaning instructions, please use this link: Cleaning Instructions for the MaxBright Diagonal.

Mechanical Features
Our customers have appreciated the brass locking ring on our adapters and 2" Barlow (BARADV)and have urged us to develop a diagonal with this feature. The recessed brass ring is under the thumbscrew location. As you tighten the thumbscrew, the brass locking ring clamps onto your eyepiece. This provides a more secure grip for your expensive eyepieces than the head of a single screw can provide. As an added advantage, the brass will not mar the surface of your accessories.

The diagonal is accurately square to the optical axis due to the CNC machined parts and special mounting method of the mirror. The baffles and flat black interior allow maximum contrast. It is threaded for 48 mm filters so that you can change eyepieces with ease without changing the filter.

Occasionally, we have a limited number of left-handed diagonals in stock. Please ask at the time you place your order. 

Important: Consider the following dimensions to be sure that the barrel of your accessories will not strike the mirror. When using 2" accessories, the depth from the top of the diagonal to the mirror surface is 1.85" (46.99 mm). When using 1.25" accessories, the depth from the top of the diagonal to the mirror surface is 2.25" (57.15 mm); our 1.25" adapter adds another 0.25" (6.35 mm) height. Remember that if you add filters to your eyepiece barrels, the overall length changes.


  • The PMDMAX has a net spacing distance of 4.1" (104.1 mm), comprised of 2.75" (69.85 mm) from the center of the ocular opening to the mirror and 1.35" (34.29 mm) from the center of the objective opening to the mirror.
  • The nosepiece net insertion depth is 1.4" (35.6 mm).

Note: Please consider our optional 1.25" Adapter (ADA125) with brass locking ring and 48 mm filter thread as the perfect compliment to the Maxbright Diagonal when using your 1.25" accessories.