Skip to content
June 24th: Store is closed for Quebec National Holiday. Orders placed that day will ship on June 25th.
June 24th: Store is closed for Quebec National Holiday. Orders placed that day will ship on June 25th.
Celestron Collimation Eyepiece 1.25 in

Celestron Collimation Eyepiece 1.25 in

by Celestron
SKU CEL-94182
$34.95 - $34.95
$34.95
$34.95 - $34.95
$34.95
Price Match Policy!
  • Precise Newtonian & SCT Collimation
  • Fits Standard 1.25" Focusers and Diagonals
  • Bright Internal Surface for Viewing Mirror Reflections
  • Integrated Crosshairs for Centering Optics
Backordered
Request Stock Alert
Availability Info
Worldwide Shipping
  • Description
  • FAQ
  • Specifications
  • In the Box
  • Warranty

  • Celestron Collimation Eyepiece - 1.25"

    The Celestron Cheshire Collimation Eyepiece provides a simple, highly accurate method for aligning the optics in your telescope. Designed to fit any standard 1.25" focuser or diagonal, this tool uses a combination of a peephole and crosshairs to ensure your Newtonian or Schmidt-Cassegrain telescope's optical components are perfectly centered for sharp, high-contrast views.

    The Cheshire Design: A Crosshair System for 1.25" Focusers

    This collimation tool operates on the elegant principle of the Cheshire eyepiece. By looking through the small peephole at the top, you view the reflection of thin crosshairs against your telescope's mirrors. The internal surfaces are brightly finished to make the faint reflections of your primary and secondary mirrors easy to see, even in low light.

    The goal is to adjust your telescope's optics until all the reflected elements, including the crosshairs, are perfectly concentric. This battery-free, robust design has no lasers to go out of alignment, making it a reliable tool for achieving and maintaining peak optical performance from your instrument.

    Newtonian and SCT Collimation: Achieving Precise Optical Alignment

    For Newtonian reflectors, the Celestron Collimation Eyepiece is an essential accessory for aligning the secondary and primary mirrors. It allows you to precisely center the secondary mirror under the focuser and then adjust the primary mirror's tilt, ensuring the entire optical path is correctly aligned for pinpoint stars across the field.

    While SCTs hold collimation well, they occasionally require fine-tuning, especially after transport. This eyepiece is helpful for confirming the alignment of an SCT by checking the concentricity of the secondary mirror's reflection, allowing you to make small adjustments for the sharpest possible planetary and deep-sky images.

    Collimation Eyepiece vs. Simple Cap: Why This Tool is More Accurate

    Many beginner telescopes include a basic collimation cap—a simple plastic cap with a central pinhole. While better than nothing, the cap lacks the precision of the Cheshire eyepiece. The Celestron Collimation Eyepiece is more accurate because its crosshairs provide a much finer reference for centering optical elements.

    • Clearer Reference: The crosshairs are easier to align perfectly than a single, often imprecise, central dot seen in a simple cap.
    • Brighter View: The side opening on the Cheshire illuminates the interior, making the reflections of your mirrors significantly brighter and easier to see than through a dark plastic cap.

  • How do I use the Celestron Collimation Eyepiece with my 8" f/5 Newtonian?

    Insert the 1.25" eyepiece into your focuser. Point the telescope at a bright surface. First, adjust your secondary mirror until the reflection of the primary mirror is centered in the crosshairs. Then, adjust the primary mirror's collimation screws until the reflection of the peephole is centered within the reflection of your primary mirror's center mark. When all reflections are concentric, you are collimated.

    Is this Collimation Eyepiece better than a laser collimator?

    Each tool has advantages. A Cheshire eyepiece like this one cannot go out of alignment itself, making it very reliable. It is also excellent for setting the secondary mirror position, which a single-beam laser cannot do. A laser is often faster for primary mirror alignment, but a misaligned laser can make your telescope's collimation worse. Many experienced astronomers use both: the Cheshire for the secondary and the laser for a quick primary check.

    How does the Celestron Collimation Eyepiece help align a Schmidt-Cassegrain (SCT)?

    For an SCT, you use this eyepiece to check the centering of the secondary mirror's reflection. While final, precise collimation of an SCT must be done on a star, this tool provides a useful daytime check to ensure the optical components are roughly aligned before you start a star test. It helps you get close, minimizing the adjustments needed at night.

    Does this 1.25" Celestron Collimation Eyepiece require batteries?

    No, it is a purely optical and mechanical tool. It uses ambient light, which enters through the cut-out on the side, to illuminate the internal crosshairs and your view of the mirrors. It requires no power to operate.

    What will I see when looking through the Collimation Eyepiece?

    You will see a series of reflections. You'll see the crosshairs of the eyepiece itself, the reflection of your secondary mirror, the reflection of the primary mirror inside the secondary, and the reflection of the eyepiece and your eye within the primary. The goal is to make all these reflections perfectly centered, like a series of nested doughnuts.

    Will this Collimation Eyepiece work with my refractor telescope?

    Generally, refractors do not require routine collimation by the user, and this tool is not designed for them. The Celestron Collimation Eyepiece is specifically designed for the optical systems of Newtonian reflectors and, to a lesser extent, Schmidt-Cassegrains.

  • Barrel Size 1.25"
    Eyepiece Type Collimation
    Warranty 2-Year Warranty
    • Celestron Collimation Eyepiece - 1.25

      Celestron Collimation Eyepiece - 1.25"

      × 1

  • Celestron 2-Year Warranty