Binorum Dielectric Advanced 99% Twist-up 2″ Diagonal Mirror
The Binorum Dielectric Advanced 99% Twist-up 2″ diagonal mirror - including a 2″/1.25″ reducer - is a precision-engineered diagonal for astronomers who refuse to lose light or contrast unnecessarily. It combines modern dielectric coating with a practical twist-up locking mechanism and an anodised aluminium body. The result is an accessory that works equally well for visual observers and astrophotographers - whether you are studying planetary detail, hunting faint nebulae, or imaging through a Cassegrain telescope.
Twist-up locking mechanism
One of the most practical features of this diagonal is the Twist-up mechanism. You secure an eyepiece or camera adapter simply by turning the red aluminium ring clockwise. Unlike a conventional thumbscrew, this mechanism applies even pressure around the entire barrel, centring the eyepiece precisely on the optical axis of the telescope. There is no risk of scratching or denting the barrel of your eyepiece or camera nose piece, and no small screw to lose in the dark. The knurled surface of the ring gives a confident grip even in winter gloves - a detail you will appreciate during cold nights under the stars.
Dielectric coating with over 99% reflectivity
A dielectric mirror with reflectivity above 99% means that almost all the light gathered by your telescope's lens or primary mirror actually reaches the eyepiece. Standard diagonals with enhanced aluminium coating typically reflect 88-92% of incoming light - the difference in image brightness is clearly visible when observing fainter objects. Dielectric layers are also far more durable: they do not oxidise, and their optical properties remain stable after years of regular use.
This diagonal is designed for use with refractors and Cassegrain telescope systems. Please note - it is not compatible with Newtonian or Dobsonian reflectors, where it would obstruct the optical path.
Solid construction, clean images
The anodised aluminium body provides mechanical rigidity at low weight. The diagonal will not strain the focuser even during long observing sessions. Internal baffles eliminate unwanted reflections and stray light. This directly improves image contrast - especially when observing planets or the Moon with ambient light nearby.
The package includes two protective caps for the inlet and outlet ports, keeping the optics clean during transport and storage. The 2″/1.25″ Twist-up reducer is also included, extending compatibility to smaller-barrel eyepieces.
What is in the box
- Binorum Dielectric Advanced 99% Twist-up 2″ diagonal mirror
- 2″/1.25″ Twist-up reducer
- Two protective caps
Technical specifications
| Parameter |
Value |
| Barrel diameter |
2″ |
| Included reducer |
2″/1.25″ |
| Deflection angle |
90° |
| Mirror coating |
Dielectric |
| Reflectivity |
>99% |
| Locking mechanism |
Twist-up |
| Body material |
Anodised aluminium |
| Compatible telescopes |
Refractors, Cassegrain systems |
| Not compatible with |
Newtonian and Dobsonian reflectors |
About Binorum
Binorum is a brand created by astronomers for astronomers. Its philosophy is to give enthusiasts accessories that genuinely meet the demands of modern observing - both visual and astrophotographic. The Binorum range of astronomy accessories includes eyepiece adapters, filters, diagonals and other components, all designed to work together and thought through to the last thread. Binorum focuses on build quality, reliable optical coatings and practical details that come from real use in the field - not from laboratory conditions. If you want accessories that will not let you down after years of regular observing, Binorum is a choice that makes sense.
Why choose a dielectric diagonal over a standard aluminium one?
A standard enhanced aluminium diagonal reflects around 88-92% of light. A dielectric diagonal reflects over 99%. That gap matters most when you are looking at faint objects - galaxies, nebulae, faint double stars. More light through means a brighter, sharper image with better colour contrast. The coating also lasts longer, so the quality you buy today is still the quality you get years from now.
Is this diagonal right for my telescope?
Yes - if you own a refractor or a Cassegrain telescope (including Schmidt-Cassegrain and Maksutov-Cassegrain). No - if you own a Newtonian or Dobsonian reflector. Those designs use a different optical path and do not use a diagonal mirror at all.
Can I use my existing 1.25″ eyepieces with this diagonal?
Yes. The included 2″/1.25″ Twist-up reducer lets you use any standard 1.25″ eyepiece straight away. You do not need to buy any extra adapter.
