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IMPORTANT: Our store is located in Canada. All orders that include products manufactured outside of Canada or USA will be subject to tariffs and duties, regardless of the order value. US customers are responsible for all applicable duties and tariffs, and those will be billed by the carrier, except for the Lacerta upgrade kit, for which we collect them at checkout.
IMPORTANT: Our store is located in Canada. All orders that include products manufactured outside of Canada or USA will be subject to tariffs and duties, regardless of the order value. US customers are responsible for all applicable duties and tariffs, and those will be billed by the carrier, except for the Lacerta upgrade kit, for which we collect them at checkout.
Baader Star Diagonal Prism w/ Zeiss Spec Prism & BBHS Coating - T-2
Baader Star Diagonal Prism w/ Zeiss Spec Prism & BBHS Coating - T-2
Baader Star Diagonal Prism w/ Zeiss Spec Prism & BBHS Coating - T-2
Baader Star Diagonal Prism w/ Zeiss Spec Prism & BBHS Coating - T-2
Baader Star Diagonal Prism w/ Zeiss Spec Prism & BBHS Coating - T-2
Baader Star Diagonal Prism w/ Zeiss Spec Prism & BBHS Coating - T-2
Baader Star Diagonal Prism w/ Zeiss Spec Prism & BBHS Coating - T-2

Baader Star Diagonal Prism w/ Zeiss Spec Prism & BBHS Coating - T-2

by Baader Planetarium
SKU BAA-2456095
$279.00 - $279.00
$279.00
$279.00 - $279.00
$279.00
Price Match Policy!
  • Zeiss-Specification Right-Angle Prism
  • Baader BBHS® (Broadband Hard Silver) Coatings
  • T-2 (M42x0.75) Threads on Input and Output Faces
  • Solid, All-Metal Housing for Maximum Rigidity
  • Ultra-Short Optical Path Design
1 in stock
Qualifies for FREE Shipping in CONUS on orders over $350.
  • Description
  • FAQ
  • Specifications
  • In the Box
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  • Warranty

  • Baader Star Diagonal Prism w/ Zeiss Spec Prism & BBHS Coating - T-2

    The Baader T-2 Star Diagonal Prism delivers superior image fidelity using a genuine Zeiss-specification prism with optical surfaces boasting a planarity approximately 5x better than standard prisms. This high-precision optic is housed in a solid metal body featuring T-2 (M42x0.75) threads on both sides, creating a rigid, versatile, and extremely short connection within any imaging or visual train.

    A Prism 5x More Precise Than Standard Designs

    At the heart of this diagonal is a right-angle prism manufactured to stringent Zeiss specifications. The planarity and conformity of the prism faces are held to a much higher standard than those found in typical diagonals, resulting in higher contrast and sharpness, especially at high magnifications. This prevents the subtle image degradation that can soften planetary details or split close double stars.

    The prism is treated with Baader's Broadband Hard Silver (BBHS®) coatings. This advanced coating system provides exceptionally high reflectivity across the visual spectrum, while a dielectric overcoat seals the silver layer, protecting it from environmental degradation and allowing for safe, gentle cleaning for a lifetime of use.

    The T-2 (M42x0.75) System: A Compact, Direct-Threaded Connection

    Unlike diagonals that rely on standard 1.25" or 2" barrels, the Baader T-2 Prism uses the Astro T-2 (M42x0.75) thread system on both its input and output faces. This design philosophy offers two key advantages: an ultra-short optical path and unparalleled system modularity. The direct-threaded connection eliminates any potential for tilt or flexure that can occur with slip-fit or compression ring holders.

    This compact, threaded body is the core of a completely customizable system. By choosing from Baader's extensive line of T-2 adapters, you can configure the diagonal for any telescope's focuser and connect any eyepiece, camera, or binoviewer with minimal added length—a critical factor for telescopes with limited back focus, such as Newtonian reflectors or refractors with focal reducers.

    Baader T-2 Prism vs. Standard 1.25" Mirror Diagonals

    While a quality mirror diagonal offers excellent views, the Baader T-2 Prism provides a distinct set of advantages for the critical observer.

    • Mirror Diagonal Advantage: A dielectric mirror diagonal is perfectly achromatic and introduces zero false color, making it an excellent choice for very fast (f/5 or below) refractors where a prism can introduce a tiny amount of chromatic aberration.
    • Baader Prism Advantage: The sealed prism surface cannot degrade over time like an exposed mirror coating can. Prisms typically exhibit less light scatter than mirrors, leading to slightly higher contrast on bright objects like the Moon and planets. Most importantly, the T-2 threaded system provides a secure, perfectly orthogonal connection that a standard 1.25" slip-fit diagonal cannot guarantee.

  • What is the advantage of the Baader T-2 Prism Diagonal's threaded connection?

    The T-2 (M42x0.75) threaded connections on both sides create a solid, flex-free optical train. Unlike standard slip-fit diagonals that can tilt slightly in the focuser, the threaded system ensures perfect alignment and orthogonality, which is critical for high-resolution imaging and visual observation.

    Will this Baader T-2 Prism Diagonal work with my Schmidt-Cassegrain Telescope?

    Yes, it is an excellent choice for an SCT. You will need the appropriate T-2 adapters to connect it to your telescope's rear cell (typically a T-2 to SCT thread adapter) and a T-2 eyepiece holder (like the Baader ClickLock) for your eyepieces. The short optical path of the prism body helps conserve precious back focus.

    Why choose the Baader T-2 Prism over a mirror diagonal for viewing Jupiter on my refractor?

    For planetary viewing on most refractors (f/6 and slower), a high-quality prism often delivers superior contrast. The prism's lower light scatter can make subtle details in Jupiter's cloud belts or the Cassini Division in Saturn's rings appear more distinct. The rigid T-2 connection also prevents any image shift when focusing at high power.

    What are Baader's BBHS® coatings on this T-2 Star Diagonal?

    BBHS® stands for Broadband Hard Silver. It's a multi-layer coating system where a layer of silver provides very high reflectivity across the entire visual spectrum. This silver layer is then protected by a hard, transparent dielectric coating, making it as durable and easy to clean as a standard dielectric mirror while retaining silver's high reflectance.

    What adapters do I need to use the Baader T-2 Prism Diagonal with 1.25" eyepieces?

    To use standard 1.25" eyepieces, you will need a T-2 eyepiece holder. Baader offers several options, with the most popular being the T-2 / 1.25" ClickLock Eyepiece Clamp (#2458100). This threads directly onto the output side of the prism diagonal and provides a secure, self-centering clamp for your eyepieces.

    Does the Baader Zeiss-spec prism introduce any color error?

    All prisms introduce a minuscule amount of chromatic aberration, as light passes through the glass. In telescopes with focal ratios of f/7 or slower, this effect is completely negligible and invisible. In very fast refractors (f/5 or faster), a trace of false color may be detectable by the most critical observers on extremely bright targets, in which case a high-quality dielectric mirror diagonal might be preferred.

  • Net weight (kg) 0.18
    Deflection angle 90°
    AR-Coating Phantom Coating® Group
    Clamping System no clamp
    Inner Diameter / Clear Aperture (mm) 34
    Optical length (mm) 38.5
    Inner Connection (eyepiece/-camera-sided) M34
    Outer Connection (eyepiece/-camera-sided) M42 x 0.75 (T-2)
    Inner Connection (lens sided) M42 x 0.75 (T-2)
    Optical Design Star Diagonal Prism
    Image Orientation Erect image, Mirror inverted
    Reflection surface Sealed BBHS coating
    Glas path 36 mm
  • Baader Planetarium Warranty