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Telescope Diagonals & Diagonal Mirrors

15 Items
Celestron 45º Correct Image Prism Diagonal - 1.25"

Celestron 1.25" 45º Correct Image Prism Diagonal - 94112-A

SKU: CEL-94112-A
  • Diagonal Type: Correct/Erect Image
  • Diagonal Size - Eyepiece Side: 1.25" Barrel
  • Diagonal Size - Telescope Side: 1.25" Barrel
$37.95

Meade 1.25" Correcting Prism 45° Diagonal for ETX-70 and ETX-80 - 07220

SKU: MEA-07220
  • Diagonal Type: Correct/Erect Image
  • Diagonal Size - Eyepiece Side: 1.25" Barrel
  • Diagonal Size - Telescope Side: 1.25" Barrel
$49.95

Meade 1.25" Erect-Image 45° Diagonal Prism - 07217

SKU: MEA-07217
  • Diagonal Type: Correct/Erect Image
  • Diagonal Size - Eyepiece Side: 1.25" Barrel
  • Diagonal Size - Telescope Side: 1.25" Barrel
$35.95
Meade 932 Erect Prism for ETX

Meade 1.25" Correcting Prism 45° Diagonal for ETX 90/105/125 - 07210

SKU: MEA-07210
  • Diagonal Type: Correct/Erect Image
  • Diagonal Size - Eyepiece Side: 1.25" Barrel
  • Diagonal Size - Telescope Side: 1.25" Barrel
$47.95
Baader 1.25" Amici Correct Image Star Diagonal

Baader 1.25" Amici Correct Image Star Diagonal - AMICI-DX1

SKU: BAD-AMICI-DX1
  • Diagonal Type: Correct/Erect Image
  • Diagonal Size - Eyepiece Side: 1.25" Barrel
  • Diagonal Size - Telescope Side: 1.25" Barrel
  • Optics Type and/or Coatings: 7-Layer Multi-Coating , Amici Prism
Free shipping Free shipping
$319.00
William Optics 45º Erect Prism - 1.25"

William Optics 1.25" 45° Erect Prism - D-EP125

SKU: WYO-D-EP125
  • Diagonal Type: Correct/Erect Image
  • Diagonal Size - Eyepiece Side: 1.25" Barrel
  • Diagonal Size - Telescope Side: 1.25" Barrel
$80.00

Stellarvue 1.25" 45° Erecting Prism - D1032

SKU: STV-D1032
  • Diagonal Type: Correct/Erect Image
  • Diagonal Size - Eyepiece Side: 1.25" Barrel
  • Diagonal Size - Telescope Side: 1.25" Barrel
$69.00
Baader 1.25" 45º Maxbright Amici Erecting Prism

Baader 1.25" Maxbright Amici 45º Erecting Prism with Integrated 2X Glass Path Corrector for MaxBright Binocular Viewers- MAXAMICI

SKU: BAD-MAXAMICI
  • Diagonal Type: Correct/Erect Image
  • Diagonal Size - Eyepiece Side: T-2 Threads
  • Diagonal Size - Telescope Side: 1.25" Barrel
  • Optics Type and/or Coatings: Amici Prism , Maxbright Coatings
$92.00

Stellarvue 2" Correct Image 45° Erecting Prism - D1035

SKU: STV-D1035
  • Diagonal Type: Correct/Erect Image
  • Diagonal Size - Eyepiece Side: 2" Barrel
  • Diagonal Size - Telescope Side: 2" Barrel
  • Includes Eyepiece Adapter: Yes, 2" to 1.25"
$209.00
Baader 2" Erecting Amici Prism Diagonal

Baader 2" 90-Degree Erecting Amici Prism Diagonal with 1.25" Adapter

SKU: BAD-AMICI-2
  • Diagonal Type: Correct/Erect Image
  • Diagonal Size - Eyepiece Side: 2" Barrel
  • Diagonal Size - Telescope Side: 2" Barrel
  • Includes Eyepiece Adapter: Yes, 2" to 1.25"
  • Optics Type and/or Coatings: 7-Layer Multi-Coating , Amici Prism
Free shipping Free shipping
$299.00
Baader Amici Erecting Prism with 24 mm Clear Aperture - 1.25"

Baader 1.25" Amici 45º Erecting Prism w/24 mm Clear Aperture - AMICI-45

SKU: BAD-AMICI-45
  • Diagonal Type: Correct/Erect Image
  • Diagonal Size - Eyepiece Side: 1.25" Barrel
  • Diagonal Size - Telescope Side: 1.25" Barrel
  • Optics Type and/or Coatings: Amici Prism
$92.00
Baader Planetarium 2" Amici 45º Erect Prism with 2" SCT Thread & 2" to 1.25" Reducer

Baader 2" Amici 45º Erecting Prism w/2" SCT Thread - AMICI-45-2

SKU: BAD-AMICI-45-2
  • Diagonal Type: Correct/Erect Image
  • Diagonal Size - Eyepiece Side: 2" Barrel
  • Diagonal Size - Telescope Side: SCT Threads
  • Includes Eyepiece Adapter: Yes, 2" to 1.25"
  • Optics Type and/or Coatings: Amici Prism
Free shipping Free shipping
$239.00
Baader Planetarium 2" 90º Astro Amici Diagonal Prism with BBHS Coating

Baader 2" Astro Amici 90º Diagonal Prism with BBHS® Coating - AMICI-DX2

SKU: BAD-AMICI-DX2
  • Diagonal Type: Correct/Erect Image
  • Diagonal Size - Eyepiece Side: 2" Barrel
  • Diagonal Size - Telescope Side: 2" Barrel
  • Includes Eyepiece Adapter: No, 1.25" Eyepiece Adapter Sold Separately
  • Optics Type and/or Coatings: Amici Prism , BBHS Coatings
Free shipping Free shipping
$719.00

William Optics 1.25” 90° Erect Prism Diagonal - D-EP90-125-II

SKU: WYO-D-EP90-125-II
  • Diagonal Type: Correct/Erect Image
  • Diagonal Size - Eyepiece Side: 1.25" Barrel
  • Diagonal Size - Telescope Side: 1.25" Barrel
$83.00

William Optics 1.25" 90° RedCat & WhiteCat Erecting Prism - Silver - D-EP90-125-RC51-SL

SKU: WYO-D-EP90-125-RC51-SL
  • Diagonal Type: Correct/Erect Image
  • Diagonal Size - Eyepiece Side: 1.25" Barrel
  • Diagonal Size - Telescope Side: 1.25" Barrel
$118.00

A star diagonal is a useful astronomy accessory because it allows viewers to look through their telescope perpendicular to the direction the telescope points or at a 45° angle. This makes diagonals handy for terrestrial observations as well. The people at High Point Scientific understand that the comfort and convenience of using a star diagonal is important to you, that is why we offer many different types of telescope diagonals for you to choose from. You will find the latest brands offering a variety of diagonals, including mirror, dielectric, and prism diagonals.


As the name suggests, mirror diagonals use a mirror to turn the telescope’s image at a 90° or 45° angle. This creates an image that is correctly oriented vertically but reversed horizontally. The mirror is typically made of silver or aluminum, both of which scratch easily. You will need to careful when cleaning and using your mirror diagonal. However, mirror diagonals are often very affordable which makes them a favorite among amateur astronomers.


Many astronomers prefer mirror diagonals but wish they were more durable. That’s why High Point Scientific also offers dielectric diagonals. Dielectric diagonals are mirror diagonals but include enhanced dielectric coatings for greater durability and reflectivity. These coatings make dielectric diagonals hard and sturdy so it is much more difficult to scratch or mar mirror surfaces.


Prism diagonals are often considered the most innovative design for a diagonal. They use a glass prism that often produces higher reflectivity than mirror or dielectric diagonals. This means that prism diagonals suffer minimal light loss to give you high contrast celestial views. Be sure to look for Amici prism diagonals on the High Point Scientific website, as these produce an upright image with a correct left-right view for low-powered eyepieces.

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