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Celestron Star Diagonal - 1.25"
Celestron Star Diagonal - 1.25"

Celestron Star Diagonal - 1.25"

by Celestron
SKU CEL-94115-A
$45.00 - $45.00
$45.00
$45.00 - $45.00
$45.00
Price Match Policy!
  • Provides a comfortable 90° viewing angle
  • Inserts into any 1.25" telescope focuser or visual back
  • Accepts standard 1.25" eyepieces
  • Corrects image orientation to be right-side-up
  • Ideal for refractors and catadioptric telescopes
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  • Description
  • FAQ
  • Specifications
  • In the Box
  • Downloads
  • Warranty

  • Celestron Star Diagonal - 1.25"

    The Celestron 1.25" Star Diagonal redirects your telescope's light path by 90°, allowing for a dramatically more comfortable viewing position. This essential accessory fits any refractor or catadioptric telescope that uses a standard 1.25" focuser and eyepieces, making it a fundamental upgrade for visual astronomy.

    The 90° Solution for Comfortable Observing

    Viewing objects near the zenith (directly overhead) without a diagonal requires crouching in an awkward, uncomfortable position that causes significant neck strain. By turning the eyepiece out to a 90° angle, this diagonal lets you observe for hours in a relaxed posture, whether you are seated or standing. This simple ergonomic improvement is critical for enjoying long sessions at the eyepiece without fatigue.

    Standard 1.25" Fit and Correct-Image Orientation

    Designed for maximum compatibility, the Celestron 1.25" diagonal slides directly into the focuser of most refractors, Schmidt-Cassegrain (SCT), and Maksutov-Cassegrain (Mak) telescopes. It also presents an image that is right-side-up, which is more intuitive for navigating the sky than the inverted view seen without a diagonal.

    • Universal Compatibility: The 1.25" barrel format is the most common standard in astronomy, ensuring this diagonal will work with a vast range of telescopes and eyepieces.
    • Image Orientation: The view is corrected vertically, so objects appear upright. The image is, however, reversed from left to right, which is standard for all mirror diagonals and is not a hindrance for astronomical observation.
    • Terrestrial Viewing Trade-off: Because of the left-right reversal, this diagonal is not recommended for terrestrial viewing where correct image orientation is required. For daytime use, an erecting prism is necessary.

  • Why do I need a star diagonal for my refractor or SCT?

    A star diagonal, like this Celestron 1.25" model, is essential for comfortable viewing. Without it, you would have to look straight through the telescope, which becomes extremely difficult and causes neck strain when observing objects high in the sky. The 90° angle allows you to look down into the eyepiece from a comfortable position.

    Will the Celestron 1.25" Star Diagonal work with my Newtonian reflector telescope?

    No. Newtonian reflectors have their focuser on the side of the tube, which is already at a comfortable 90° angle. Adding a star diagonal would not only be redundant but would also push the eyepiece out too far, preventing the telescope from reaching focus.

    What does "right side up, but reversed left-to-right" mean when viewing the Moon with this diagonal?

    When you observe the Moon through the Celestron 1.25" Star Diagonal, craters and seas will appear upright, just as you see them with your naked eye. However, the left and right sides will be swapped. For example, the Sea of Tranquility (Mare Tranquillitatis), which is on the eastern limb (left side from the northern hemisphere), will appear to be on the right side of the lunar disc.

    Can I use this Celestron 1.25" diagonal for bird watching?

    It is not recommended. While the image will be upright, the left-to-right reversal makes it very difficult to follow moving objects like birds or boats. For terrestrial viewing, you should use a 45° or 90° "correct-image" or "erecting" prism diagonal, which corrects the view on both axes.

    Does the Celestron 1.25" Star Diagonal affect the focus of my telescope?

    Yes, all diagonals add to the optical path length. Refractor and catadioptric (SCT, Mak) telescopes are designed with enough focus travel to accommodate a diagonal. You will simply need to adjust the focuser to achieve a sharp image. This diagonal will not cause any issues with reaching focus on a compatible telescope.

    What telescopes are compatible with the Celestron 1.25" Diagonal?

    This diagonal is compatible with any telescope that uses a 1.25" focuser and does not have a built-in diagonal. This includes most:

    • Refractor telescopes
    • Schmidt-Cassegrain telescopes (SCTs)
    • Maksutov-Cassegrain telescopes (Maks)
  • Barrel Size 1.25"
    Viewing Angle 90°
    Image Orientation Right side up, reversed left-to-right
    Compatible Telescope Designs Refractors, Schmidt-Cassegrain, Maksutov-Cassegrain
    • Celestron 1.25 inch Star Diagonal

      Celestron 1.25" Star Diagonal

      × 1

    • Dust caps for 1.25 inch diagonal

      Dust Caps

      × 2

  • Celestron 2-Year Warranty