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Baader Hyperion Aspheric 72° 31mm Eyepiece - 1.25"/2"
Baader Hyperion Aspheric 72° 31mm Eyepiece - 1.25"/2"
Baader Hyperion Aspheric 72° 31mm Eyepiece - 1.25"/2"
Baader Hyperion Aspheric 72° 31mm Eyepiece - 1.25"/2"
Baader Hyperion Aspheric 72° 31mm Eyepiece - 1.25"/2"
Baader Hyperion Aspheric 72° 31mm Eyepiece - 1.25"/2"
Baader Hyperion Aspheric 72° 31mm Eyepiece - 1.25"/2"

Baader Hyperion Aspheric 72° 31mm Eyepiece - 1.25"/2"

by Baader Planetarium
SKU BAA-2454631
$290.00 USD - $290.00 USD
$290.00 USD
$290.00 USD - $290.00 USD
$290.00 USD
Price Match Policy!
  • 31mm Focal Length
  • 72° Apparent Field of View (in 2" mode)
  • Aspheric Optical Design with 6 Lens Elements
  • Dual 1.25" and 2" Barrel Design
  • 17mm Eye Relief
  • M43 and SP54 Camera Threads for Eyepiece Projection
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  • Baader Hyperion Aspheric 72° 31mm Eyepiece - 1.25"/2"

    The Baader Hyperion Aspheric 31mm is a 2" wide-field eyepiece with aspheric lens surfaces: 6 elements in 4 groups, a 72° apparent field and a 38mm field stop with the 2" barrel, and 17mm of eye relief. It is delivered with 1.25" and 2" plug-in sleeves (with the 1.25" sleeve the field is 55° and the field stop 30mm). M43 and SP54 system threads allow eyepiece projection, a 2" SC thread in the body lets it screw directly onto a Schmidt-Cassegrain, and Baader Phantom Coating Group anti-reflection coatings are used.

    The Hyperion Aspheric Concept: High Contrast at 72°

    The 72° field is only slightly larger than the largest viewing angle of the human eye (68°), so the entire star field can be surveyed at once without having to roll the eyes.

    Baader argues that in eyepieces with fields of 80° and more the field cannot be taken in at once and the available light is spread over too large an area, and it lists a higher limiting star magnitude and low weight among the advantages of the Aspheric design.

    Aspheric Optics: 6 Elements for Edge-to-Edge Sharpness

    At the core of the Hyperion 31mm is an aspheric optical system. In an uncorrected system rays near the edge are refracted differently from rays near the axis, so the field can blur towards the edge; aspheric correction resolves numerous imaging errors at once, giving sharpness over the entire field with reduced distortion. Aspheric surfaces are now standard in modern camera lenses.

    The aspheric construction allows fewer glass surfaces, and together with the Phantom Group coating this gives a brighter, more contrast-rich image.

    Phantom Coating® Group: 7-Layer Coatings for Peak Visual Sensitivity

    Every glass-to-air surface in the Hyperion Aspheric 31mm is treated with Baader's Phantom Coating® Group, a 7-layer broadband anti-reflection coating. Each coating stack is calculated for the specific glass type of the lens it is applied to. The system is optimized to be most effective where the dark-adapted human eye is most sensitive: around 520nm, in the green part of the spectrum.

    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, so that the least light is lost for the night-adapted eye.

    Dual 1.25" & 2" Barrels with a 2" SC Thread

    The Hyperion Aspheric 31mm is delivered with both 1.25" and 2" plug-in sleeves. In the 2" configuration, it delivers the full 72° apparent field of view with a 38mm field stop. When using the 1.25" barrel, the field is reduced to 55° with a 30mm field stop.

    On the telescope side there is a 2" SC thread in the eyepiece body, so the eyepiece can be screwed directly onto the end of the tube of a Schmidt-Cassegrain, without a plug-in sleeve and without a star diagonal. Visually, this very short attachment gives a larger true field of view than a wide-angle eyepiece with a 2" plug-in sleeve.

    M43 & SP54 System Threads for Eyepiece Projection

    Each Aspheric eyepiece has screw threads on both sides so it can be installed as a projection system in an optical beam path. On the eye side, DSLR camera bodies can be attached directly behind the eyepiece using the M43 or SP54 system thread, and the telescope's effective focal length can then be changed almost arbitrarily when small star fields or planets are to be recorded at high resolution.

    For afocal photography, Baader's digiscoping guide lists DT-rings that adapt the SP54 thread to camera filter threads from M28 to M62 (for example SP54/M28 #2958028 and SP54/M62 #2958062; some need the 11mm extension ring #2958090).

    Two-Eyed Viewing: Binoviewing with a 59.5mm Diameter

    The Aspheric eyepieces can also be used on astro-binoculars, and in any telescopic binocular where the minimum eye distance is not less than 56mm. The outer diameter is 59.5mm.

    The 31mm is also in the parfocal group.

    Build and Ergonomics: A 0.40 kg Body with 17mm of Eye Relief

    The listed net weight is 0.40 kg; the design data gives 356g with the 2" barrel and 365g with the 1.25" barrel. Eye relief is 17mm, and the eyecup is a folding eyecup on the M43 thread. The drawing gives 76.7mm for the body above the reference plane with the 2" barrel (27.5mm), and 92.2mm with the 1.25" barrel (23.9mm).

    Wide-angle eyepieces with very large fields or simple lens construction often give a nervous view, where the field disappears if the eye moves slightly, and this is frustrating when sharing views with students and guests.

  • Why does the Aspheric have a 72° field?

    A 72° field is only slightly larger than the largest viewing angle of the human eye (68°), so the whole field can be surveyed without rolling the eyes, while in fields of 80° and more the available light is spread over too large an area.

    How does the dual 1.25" and 2" barrel system on the Hyperion 31mm Aspheric work?

    The eyepiece comes with two interchangeable barrels. Using the 2" barrel provides the full 72° apparent field of view with a 38mm field stop. When you switch to the 1.25" barrel, the field of view is reduced to 55° with a 30mm field stop.

    Can I use the Baader 31mm Aspheric eyepiece for astrophotography?

    Yes. The eyepiece is designed for eyepiece projection. It features an M43 thread and an SP54 system thread on the eye lens side. DSLR camera bodies can be attached directly behind the eyepiece through these threads, using Baader adapter rings.

    What magnification does the 31mm give?

    Magnification is the telescope's focal length divided by 31. On a telescope of 1000mm focal length it gives about 32x. Exit pupil is the eyepiece focal length divided by the telescope's focal ratio; at f/10 it is 3.1mm.

    What is the benefit of the 2" SC thread on the Baader 31mm Aspheric?

    The integrated 2" Schmidt-Cassegrain thread lets you attach the eyepiece directly to the back of an SCT, eliminating the need for a diagonal. This very short attachment gives a larger true field of view than a wide-angle eyepiece with a 2" plug-in sleeve.

    Is the 31mm parfocal with the 36mm Aspheric?

    Baader's technical data lists both Aspheric focal lengths in the parfocal column. The field stop of the 31mm sits at the reference plane (0mm) with the 2" barrel.

    What makes the "Phantom Group" coatings on the Baader 31mm Aspheric special?

    Baader's Phantom Group coating is a 7-layer broadband anti-reflection coating with extremely low residual reflection, calculated for each glass type and optimised for about 520nm, where the night-adapted eye is most sensitive.

    Is the 17mm eye relief of the Hyperion Aspheric 31mm sufficient for eyeglass wearers?

    Eye relief is 17mm and the eyecup is a folding type. Baader makes no specific statement about eyeglass use for this eyepiece.

    Can I use the Baader 31mm Aspheric in a binoviewer?

    Yes. The eyepiece has an outer diameter of 59.5mm, and it can be used in any telescopic binocular where the minimum eye distance is not less than 56mm.

    What does Baader say about the weight?

    The listed net weight is 0.40 kg. The design data sheet gives 356g with the 2" barrel and 365g with the 1.25" barrel; the technical data are based on optical design data.

  • Focal Length 31mm
    Apparent Field of View 72° (2" barrel); 55° with the 1¼" barrel
    Barrel Size 1.25" and 2"
    Net weight (kg) 0.40
    Eye Relief (mm) 17 mm
    Field Stop Diameter 38 mm (2"), 30mm (1¼")
    Number of Lens Elements 6
    Parfocal Eyepieces Yes
    AR-Coating Phantom Coating® Group
    Optical Design Aspheric
    Speciality Eyepiece projection: classical
    Threaded for filters Yes
    Field Stop Displacement to reference plane +/- 0 mm
    Number of Groups 4
    Dustcaps 1¼" dustcap (31.8mm), 2" dustcap (45mm), 2" dustcap (46.5mm - fits over eyecup)
    Eyecups folding eyecup (M43)
    Slip Protect Safety Classic Undercut
    Eyepiece Body above Reference Plane (mm) 76.7 mm
    Length of 1¼" barrel (mm) 23.9 mm
    Length of 2" barrel (mm) 27.5 mm
    Eyepiece Series Hyperion
    Outer Diameter 59.5 mm
    Camera Thread M43, SP54

    • Baader Hyperion Aspheric 72° 31mm Eyepiece

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