Kasai Eyepieces and Barlows

Premium Japanese Hand-crafted Optics

Orthoscopic Eyepieces

These eyepieces are based on the classic Abbe Orthoscopic (3 + 1 element) design. The 3 cemented elements are hand-aligned by Japanese craftsmen. Fully multicoated lenses provide clean, high-contrast images suitable for optimum planetary and lunar viewing.

Technical specs:

  • Apparent Field-of-View: 42°
  • Focal lengths: 5mm / 6mm / 7mm / 9mm / 12mm / 18mm
  • Eye relief: ~80% of focal length


Astroplan Eyepieces

Optics based on Carl Zeiss 2 + 1 + 2 super Plossl design which creates a flatter image field and 20% larger apparent FOV than the Abbe Ortho while maintaining the Ortho's sharpness and contrast.

Technical specs:

  • Apparent Field-of-View: 50°
  • Focal lengths: 5mm / 7.5mm / 10mm / 12.5mm / 15mm / 20mm
  • Eye relief: ~85% of focal length


Extra-wide-vue Eyepieces

Extra-wide-vue eyepieces are rich-field eyepieces based on fully multi-coated Erfle-based 5-element eyepieces, but modified for an extra-wide FOV by Kasai.

Technical specs:

  • Apparent Field-of-View: 85°
  • Focal lengths: 10mm / 16mm (1-1/4" eyepieces) and 20mm / 26mm / 32mm (2" eyepieces)
  • Eye relief: ~60% of focal length



These barlows are optimized for fast (small F-ratio) telescopes, improving objective aberrations while lengthening the focal length of the scope. They are well-matched to Abbe Ortho or Astroplan eyepieces and available in 1.5x and 2x magnifications for 1-1/4" or 2" eyepieces.