Baader Hyperion 68° 17mm Eyepiece - 1.25"/2"

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

The Hyperion 17mm optical design uses 8 lens elements arranged in 5 groups with a 68° apparent field of view and a 20.3mm field stop (Baader technical data). Baader sums up the series as offering ease of view even at high magnifications.

Eye relief is 20mm. The folding eyecup sits on the M43 thread; it can be stored folded down, especially for persons who wear glasses, or folded up.

Baader Phantom Coating® Group for Maximum Contrast

Every air-to-glass surface within the Hyperion 17mm eyepiece is treated with Baader's 7-layer Phantom Coating® Group broadband anti-reflection coatings. A strong green reflex shows light between 500 and 550 nm being reflected and lost, while Phantom Group coatings appear almost colourless, showing an equally good effect across the visible spectrum.

This coating system is specifically optimized for the wavelengths where the night-adapted human eye has its highest sensitivity, around 520 nm. Baader's aim is that the least amount of light is lost for a night-adapted eye, without stray light.

Dual 1.25" and 2" Barrel System

The Hyperion 17mm works as both a 1.25" and a 2" eyepiece. The eyepiece comes standard with a 28mm long 1.25" barrel that contains the first lens group. 1.25" filters (M28.5) screw onto this barrel, and its slip protection is a classic undercut.

By unscrewing the entire 1.25" barrel assembly, you expose the main body's integrated 51.5mm long 2" barrel. This allows the eyepiece to be used in a 2" focuser or diagonal. An M48 thread is located between the 1.25" and 2" sections, allowing a 2" filter to be installed internally, which also modifies the focal length.

Achieving 13.1mm, 10.8mm, and 9.2mm with Finetuning Rings

A core feature of the Hyperion's modular design is the ability to change its focal length. By unscrewing the 1.25" barrel, which holds the front lens group, you can insert optional Baader Finetuning Rings (FTRs) between it and the main eyepiece body. This changes the spacing of the optical elements, resulting in a shorter focal length and higher magnification without adding any new lenses to the light path, which is unavoidable with a Barlow lens.

• With 14mm FTR: The focal length becomes 13.1mm.
• With 28mm FTR: The focal length becomes 10.8mm.
• With 14mm + 28mm FTRs: The focal length becomes 9.2mm.
• With a 2" Filter: Inserting a Baader 2" eyepiece filter of 6mm height between the barrel sections changes the focal length to 14.6mm.

This system allows you to effectively get multiple eyepieces from a single one, fine-tuning the magnification for different targets or seeing conditions without loss of sharpness.

M43 and SP54 System Threads for Classical and Afocal Projection

All Hyperion eyepieces are suitable for afocal and classical eyepiece projection. By removing the rubber eyecup and thread-protecting ring, two distinct male threads are revealed, providing a secure, direct-coupled interface for cameras.

• M43 System Thread: This inner thread is intended for "classical" eyepiece projection. With the Hyperion M43/T-2 ring (#2958080), the Baader Astro T-2 System adapters for Moon and planetary photography can be used, and any T-2 camera ring with an SLR or DSLR camera may be attached.
• SP54 System Thread: This larger outer thread is designed for "afocal" projection, where a camera with a non-removable lens (like a point-and-shoot camera or camcorder) images the view produced by the eyepiece. Baader DT-rings such as SP54/M28 (#2958028) and SP54/M37 (#2958037), used with the Hyperion 11mm extension ring (#2958090), adapt this SP54 thread to the filter thread on the front of a camera lens.

Build, Parfocal Group and Binocular Use

Net weight is 0.41 kg and the outer diameter 58mm; the design data gives 385g for the eyepiece. The drawing gives 58.8mm for the body above the reference plane, 28mm for the 1.25" barrel and 51.5mm for the 2" barrel. The 17mm belongs to the parfocal group of the series, together with the other focal lengths except the 24mm.

The winged rubber eyeshield of the Hyperion 68° eyepieces is ideal for binocular use. Only open the eyepiece 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).