Skip to content
Until May 2nd, 2025, orders under US$800 will not incur any duties or taxes upon delivery. Please note that orders under US$800 crossing the Canada-USA border after this date will be subject to duties. They will be billed by the carrier, and you will be responsible to pay them. Prioritize ordering items that are in stock!
Until May 2nd, 2025, orders under US$800 will not incur any duties or taxes upon delivery. Please note that orders under US$800 crossing the Canada-USA border after this date will be subject to duties. They will be billed by the carrier, and you will be responsible to pay them. Prioritize ordering items that are in stock!

Features

  • A great accessory for daytime terrestrial viewing with your telescope
  • This 1.25" diagonal produces right side up and left-to-right correct images when used with refractors and catadioptric (Schmidt-Cassegrain) telescopes
  • Inserts into 1.25" focusers or visual backs; accepts standard 1.25" eyepieces

Celestron 45-Degree Erect Image Diagonal

Did you know that most telescopes work well for daytime viewing as well as for astronomy? If you have a refractor or a catadioptric telescope (the Schmidt-Cassegrain is the most popular example), and you would like to use it for terrestrial observations, the most useful additional accessory you can buy is an erect-image diagonal.

If you look through your telescope with the standard mirror or star diagonal installed, you will notice that objects may be either upside down, flipped so that you see a mirror image, or a combination of the two. This is fine for observations of celestial objects, but it can be a little confusing when you are trying to track a boat as it moves through the water, or an eagle as he flies towards his perch.

Luckily, this is an easy problem to correct. Simply remove the standard diagonal from the telescope’s focuser or visual back, and install the Celestron 45º Erect Image Diagonal. Now, when you insert an eyepiece, objects will be right side up and left-to-right correct. The 45º angle of this Amici prism diagonal is very comfortable for daytime observations, where the telescope is often in a horizontal position.

Please Note: Adding an erect-image diagonal to a Newtonian reflector will not result in images that are right side up and left-to-right correct. The optical design of a Newtonian will always produce images that are rotationally off in orientation. This does not mean that you can’t use a Newtonian reflector during the day, it just means that you have to get used to objects oriented in unrealistic positions.

You may also like

  • $92.00 USD - $92.00 USD
    $92.00 USD
    $92.00 USD - $92.00 USD
    $92.00 USD

    William Optics 45° Erecting Prism - 1.25"

    WO-D-EP125

    45-degree erecting prism for 1.25" telescope eyepieces Provides correct image orientation for terrestrial and astronomical viewing Des...

    View full details
    $92.00 USD - $92.00 USD
    $92.00 USD
    $92.00 USD - $92.00 USD
    $92.00 USD
  • $249.95 USD - $249.95 USD
    $249.95 USD
    $249.95 USD - $249.95 USD
    $249.95 USD

    Celestron Dielectric Star Diagonal with Twist-Lock - 2"

    CEL-93573
    Only 3 left!

    Features Enjoy better views through your telescope with this premium diagonal featuring diffraction-limited optics and dielectric coatings Provides...

    View full details
    $249.95 USD - $249.95 USD
    $249.95 USD
    $249.95 USD - $249.95 USD
    $249.95 USD
  • $96.00 USD - $96.00 USD
    $96.00 USD
    $96.00 USD - $96.00 USD
    $96.00 USD

    William Optics 90° Erect Prism - 1.25"

    WO-D-EP90-125II

    90-degree erecting prism for 1.25" telescope eyepieces Provides correct image orientation for terrestrial and astronomical viewing Des...

    View full details
    $96.00 USD - $96.00 USD
    $96.00 USD
    $96.00 USD - $96.00 USD
    $96.00 USD
  • $339.95 USD - $339.95 USD
    $339.95 USD
    $339.95 USD - $339.95 USD
    $339.95 USD

    Celestron Off-Axis Guider

    CEL-93648
    Only 1 left!

    Features Most accurate way to guide – improved accuracy compared to using a separate guide scope 12.5mm multi-coated prism with optimized performan...

    View full details
    $339.95 USD - $339.95 USD
    $339.95 USD
    $339.95 USD - $339.95 USD
    $339.95 USD
  • $92.00 USD - $92.00 USD
    $92.00 USD
    $92.00 USD - $92.00 USD
    $92.00 USD

    Baader 45° Amici Prism Diagonal w/ 24mm Clear Aperture - 1.25"

    BAA-2956150

    Much larger prism than other so-called "Erecting prisms" Many Erect image prisms have only 19 mm free passage opening and therefore are not suitab...

    View full details
    $92.00 USD - $92.00 USD
    $92.00 USD
    $92.00 USD - $92.00 USD
    $92.00 USD