Baader Hyperion 68° 13mm Eyepiece - 1.25"/2"

An 8-Element, 68° Field with 20mm of Eye Relief

The Hyperion 13mm uses 8 lens elements arranged in 5 groups, with a 68° apparent field, 20mm of eye relief and a 15.4mm field stop (Baader technical data). Baader sums up the series as offering ease of view even at high magnifications, and notes that the rubber eye cap can be stored folded down, especially for persons who wear glasses.

Baader's technical data lists the 13mm in the parfocal group of the series, together with the other focal lengths except the 24mm. Parfocal eyepieces need little refocusing when exchanged.

Baader Phantom Group Coatings Optimized for 520nm

Every air-to-glass surface in the Hyperion 13mm is treated with Baader's proprietary 7-layer Phantom Group broadband anti-reflection coatings. Baader optimised the coatings to be most effective where the night-adapted eye is most sensitive, at about 520nm in the green part of the spectrum.

• Per glass type: an anti-reflection layer system was worked out for each type of glass in the Hyperion eyepieces.
• Almost colourless: A strong green reflex shows light between 500 and 550 nm being reflected and lost; Phantom Group coatings appear almost colourless, showing an equally good effect across the visible spectrum.
• Aim: the least amount of light lost for a night-adapted eye, without stray light, with extremely low residual reflection.

Dual 1.25" and 2" Barrels

The Hyperion 13mm comes with both 1.25" and 2" barrels. The 1.25" barrel fits 1.25" focusers and diagonals, and 1.25" filters screw onto it. For telescopes equipped with a 2" focuser, the entire 1.25" barrel section, which houses the first lens group, simply unscrews.

This reveals the included 2" barrel. The M48 thread between the 1.25" and 2" barrels takes a 2" filter; with a Baader 2" eyepiece filter of 6mm height in place, the focal length becomes 11.7mm. Both barrels have a classic undercut as slip protection.

Modular Focal Lengths: From 13mm down to 8.1mm

A key feature of the Hyperion series is its ability to change focal length without a Barlow lens. By unscrewing the 1.25" barrel, you can insert Baader's optional 14mm or 28mm Finetuning Rings (FTRs) between the main eyepiece body and the front lens group. This alters the spacing of the optical elements, reducing the effective focal length and increasing magnification.

• With 14mm FTR: The focal length becomes 10.8mm.
• With 28mm FTR: The focal length becomes 9.2mm.
• With 14mm + 28mm FTRs: The focal length becomes 8.1mm.

This modularity allows you to fine-tune the magnification for specific targets or seeing conditions without introducing additional lenses into the beam, as is unavoidable with a Barlow lens.

M43 and SP54 Threads for Projection and Afocal Imaging

Beneath the rubber eye cap and the large silicone thread-protecting ring are two system threads for attaching cameras. All Hyperion eyepieces are suitable for afocal and classical eyepiece projection.

• M43 Thread (Classical Projection): Removing the eye cap exposes the M43 male thread. With the Hyperion M43/T-2 ring (#2958080), the Baader Astro T-2 System adapters can be used, and any T-2 camera ring with an SLR or DSLR camera may be attached. In this setup, the eyepiece projects a magnified image directly onto the camera sensor.
• SP54 Thread (Afocal Imaging): Beneath a protective silicone ring lies a larger SP54 thread. This is designed for afocal photography, where a camera with its own lens still attached (like a point-and-shoot or video camera) is mounted to the eyepiece. Hyperion DT-rings such as SP54/M28 (#2958028) and SP54/M37 (#2958037), used with the Hyperion 11mm extension ring (#2958090), adapt the SP54 thread to the camera's front filter thread.

Build, Opening Rule and Spotting Scope Use

The body has an outer diameter of 58mm; the drawing gives 62.1mm above the reference plane, 24mm for the 1.25" barrel and 47.5mm for the 2" barrel, and the design data gives 387g (our specification table gives a net weight of 0.41 kg). Without the first group of lenses the eyepiece becomes a 2" eyepiece of 22.9mm focal length; use this only for afocal projection imaging, since visual use shows a loss of edge sharpness.

Baader asks that the eyepiece only be opened at the M48 thread at the top of the 1.25" barrel; other joints are secured with Loctite, and disassembly elsewhere voids the warranty. Hyperion 68° eyepieces can also be used on Zeiss Diascope spotting scopes with the Baader Diascope bayonet 1.25" adapter (#2454500), and on Zeiss Harpia spotting scopes with the Harpia 85/95 adapter (#2454511).