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Silver cylindrical 1.25 inch eyepiece with black rubber guard

Baader Planetarium

Baader Planetarium 17mm Hyperion Modular Eyepiece 1.25" 20mm Eye Relief Rubber Guard

SKU CH-T5YY-WWHER

A 17mm eyepiece with 68° apparent field, 20mm eye relief and 1.25" barrel fits many telescopes and accepts standard filters

  • Fully multi-coated optics deliver bright, high-contrast images
  • 20 mm eye relief enables comfortable viewing with glasses
  • 25" barrel with M28.5 x 0.6 and M48 x 0.75 threads fits many telescopes
  • 68° apparent field of view gives immersive wide-field observation
  • Modular Hyperion design supports photo-visual versatility

Product identity and intended user

The Baader Planetarium 17mm Hyperion eyepiece provides a 68° apparent field of view with 20mm eye relief for comfortable, immersive observation. It is suited to astronomy enthusiasts who want wide, flat-field performance without a premium price tag.

Practical limits of the 1.25" interface

The 1.25" barrel restricts the maximum field stop compared with larger formats, capping true wide-angle potential at longer focal lengths. Standard M28.5 x .6 and M48 x .75 filter threads accept common astronomy filters, but the barrel diameter itself remains the limiting factor.

Upgrade path and when it matters

This eyepiece replaces narrower Plössl or Kellner designs, delivering a noticeably wider 68° view and longer eye relief for spectacle wearers. The jump is worthwhile when you want expansive, high-contrast fields in fast telescopes without moving to 2" hardware.

Highlights

  • Fully multi-coated optics deliver bright, high-contrast images
  • 20 mm eye relief enables comfortable viewing with glasses
  • 25" barrel with M28.5 x 0.6 and M48 x 0.75 threads fits many telescopes
  • 68° apparent field of view gives immersive wide-field observation
  • Modular Hyperion design supports photo-visual versatility

Specifications

No published specifications for this item yet.

Questions about this item

How do I choose between the 1.25 inch barrel and the M28.5 or M48 filter threads?

The 1.25 inch barrel fits standard telescope focusers. The M28.5 x 0.6 and M48 x 0.75 threads accept standard astronomy filters directly on the eyepiece.

What does the 68 degree apparent field of view mean when I look through the 17mm eyepiece?

A 68 degree apparent field gives a wide, immersive window on the sky, showing a large swath of sky in a single view without moving the telescope.

Will the M48 x 0.75 thread work with my 2 inch filter drawer or does it cap at 1.25 inch filters?

The M48 x 0.75 thread accepts 48mm filters, which are larger than 1.25 inch mounted filters, so it is not limited to the smaller filter size.

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