Baader T-2 90° 32mm Prism Diagonal with 1.25" Nosepiece and Eyepiece Holder # PRISM-1 2456005K

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Our Product ID: ODIA-BP-PRISM-1
Manufacturer SKU: PRISM-1
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Baader T-2 90° 32mm Prism Diagonal with 1.25" Nosepiece and Eyepiece Holder # PRISM-1 2456005K

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Quick Overview

  • Precision-engineered prism-based star diagonal offers minimal light scatter for high-contrast planetary views at high magnification
  • Ideal for compound telescopes and refractors with focal ratios longer than f/7
  • Offers a compact size and short optical path where space is at a premium and short back focus is essential
  • Reconfigurable with other Baader T-2 nosepieces and eyepiece holders to suit a wide range of telescopes and applications that require the full 32mm clear aperture of the prism
  • Superb mechanical fit and finish

Product Details

Star diagonals that use glass prisms as the main reflective component have many advantages over mirror-based diagonals. They have shorter optical path lengths. They exhibit minimal light scatter and they provide high contrast images. And, when well made, their reflective properties do not degrade with age.

Baader Planetarium has worked hard to make the finest and most precisely-engineered prism-based star diagonals on the market today. This Baader T-2 90° Prism Diagonal #2456005K includes the Baader T-2 90-degree diagonal body with 32mm clear aperture, which itself is available as a stand-alone component (T2-01C). It also includes a 1.25" nosepiece (T2-14) and a premium 1.25" eyepiece holder (EYEHOLD-2)  from Baader's T-2 system of accessories. The nosepiece includes standard 1.25" filter threads, while the eyepiece holder includes dual clamp screws, a non-marring compression ring, and a rotating helical focuser for fine focus adjustment. Rotating this focuser will also rotate the eyepiece or accessory in the focuser.

The optics-grade glass prism in this Baader diagonal is precisely ground to the correct angles for maximum reflectivity and polished to minimize loss and scatter at the air-glass interface. The prism is multi-coated to minimize loss, then mounted in a precisely machined aluminum housing to ensure that the glass remains in the correct location and orientation for maximum performance and long life.

This Baader diagonal works well for observing nearly all celestial objects. But since it minimizes scattered light and wavefront error, it's especially good for high-contrast and high-magnification planetary and double-star observation with Schmidt-Cassegrain and Maksutov-Cassegrain telescopes and with refracting telescopes of focal ratio longer than f/7. While this 1.25" diagonal works with telescopes of shorter focal ratio, especially when observing fainter objects, the steeper angles at which light passes through the prism may cause some chromatic aberration when observing planets and other bright objects in faster refractors.

The smaller size of this 1.25" diagonal is a great advantage with smaller fork-mounted compound telescopes where larger 1.25" and 2" diagonals cannot ‘swing through’ the fork. Its shorter optical path length (64mm / 2.52" including nosepiece and eyepiece holder)  is also a big advantage where shorter back focus is required such as when observing with Baader's MaxBright binoviewers.

And since the 1.25" T-2 nosepiece and eyepiece holder of this diagonal are removable, you can swap them out for other components in the Baader T-2 suite of accessories to adapt the diagonal to other telescopes and applications. The diagonal body itself has a T/T2 female thread on the telescope side and a T/T2 male thread on the eyepiece side.

NOTE: Like mirror-based star diagonals, but unlike diagonals with an Amici prism, this diagonal gives images that are upright but left-right reversed.

Manufacturer part number: PRISM-1 or 2456005K.