Skip to content



William Optics 90° Erect Prism - 1.25"

Original price CA$130.00 - Original price CA$130.00
Original price
CA$130.00 - CA$130.00
Current price CA$130.00
Credit available from affirm logo


  • 90-degree erecting prism for 1.25" telescope eyepieces
  • Provides correct image orientation for terrestrial and astronomical viewing
Contact us to know when we will receive our next ones!

Free Shipping on most orders above $500*

More information

  • Description
  • The William Optics 90° Erect Prism - 1.25" is a versatile optical accessory designed to provide comfortable viewing angles and correct image orientation for both terrestrial and astronomical observations. This high-quality prism is compatible with 1.25" eyepieces and telescopes, offering enhanced versatility for various observing scenarios.


    Designed for use with 1.25" eyepieces and telescopes with 1.25" focusers. Not compatible with 2" equipment without additional adapters.

    Optical Performance

    Features high-quality optical glass and coatings to ensure bright, clear images with minimal light loss. The erecting prism design provides a fully corrected image orientation, making it ideal for both terrestrial and celestial observations.

    William Optics 90° Erect Prism - 1.25


    William Optics 90° Erect Prism - 1.25

    Built with durable materials to ensure long-lasting performance and reliability. The precision-machined housing provides secure connections and maintains proper alignment of the optical elements.


    Designed for use with 1.25" eyepieces and telescopes with 1.25" focusers. The prism features standard 1.25" fittings on both the eyepiece and telescope sides, ensuring wide compatibility with most refractors, reflectors, and catadioptric telescopes.

    Comfort and Ergonomics

    The 90-degree design provides a comfortable viewing position, especially for observations near the zenith. This ergonomic design reduces neck strain during extended observing sessions, making it ideal for both casual stargazing and prolonged study of celestial objects.

    Image Orientation

    Unlike standard star diagonals, this erecting prism provides a fully corrected image orientation - right-side-up and correctly oriented left-to-right. This feature is particularly valuable for terrestrial observations and for easily locating and tracking celestial objects.


    Suitable for a wide range of observations, from daytime terrestrial viewing to nighttime astronomical observations. The correct image orientation makes it especially useful for nature watching, spotting scopes, and for easily following star charts during astronomical sessions.

    Optical Coatings

    Features high-quality anti-reflection coatings to maximize light transmission and reduce unwanted reflections. These coatings help maintain image brightness and contrast, crucial for observing faint celestial objects.

    Ease of Use

    Designed for quick and easy installation and removal. The smooth, precise fit ensures that changing between direct viewing and prism use is hassle-free, allowing for flexibility during observing sessions.