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Telescope Diagonals & Diagonal Mirrors

23 Items
Apertura 1.25" Carbon Dielectric Diagonal Full View

Apertura 1.25" Carbon Dielectric Mirror Diagonal - D1CF

SKU: APT-D1CF
  • Diagonal Type: Mirror Diagonal
  • Diagonal Size - Eyepiece Side: 1.25" Barrel
  • Diagonal Size - Telescope Side: 1.25" Barrel
  • Includes Eyepiece Adapter: No, 1.25" Eyepiece Adapter Sold Separately
  • Optics Type and/or Coatings: Dielectric Coatings
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$79.95
Celestron 1.25" Dielectric Star Diagonal with Twist-Lock

Celestron 1.25" Dielectric Star Diagonal with Twist-Lock - 93571

SKU: CEL-93571
  • Diagonal Type: Mirror Diagonal
  • Diagonal Size - Eyepiece Side: 1.25" Barrel
  • Diagonal Size - Telescope Side: 1.25" Barrel
  • Optics Type and/or Coatings: Dielectric Coatings
$131.95
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
Celestron 90º Prism Star Diagonal - 1.25"

Celestron 1.25" 90º Prism Star Diagonal - 94115-A

SKU: CEL-94115-A
  • Diagonal Type: Prism Diagonal
  • Diagonal Size - Eyepiece Side: 1.25" Barrel
  • Diagonal Size - Telescope Side: 1.25" Barrel
$38.95

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

Meade 918A Diagonal Mirror - 1.25" - 07202

SKU: MEA-07202
  • Diagonal Type: Mirror Diagonal
  • Diagonal Size - Eyepiece Side: 1.25" Barrel
  • Diagonal Size - Telescope Side: 1.25" Barrel
$28.95

Tele Vue 1.25" 60 Degree Everbrite Mirror Diagonal - DPC-6012

SKU: TLV-DPC-6012
  • Diagonal Type: Mirror Diagonal
  • Diagonal Size - Eyepiece Side: 1.25" Barrel
  • Diagonal Size - Telescope Side: 1.25" Barrel
  • Optics Type and/or Coatings: Everbrite Coatings
$234.95

Tele Vue 1.25" 90 Degree Everbrite Mirror Star Diagonal - DPC-1250

SKU: TLV-DPC-1250
  • Diagonal Type: Mirror Diagonal
  • Diagonal Size - Eyepiece Side: 1.25" Barrel
  • Diagonal Size - Telescope Side: 1.25" Barrel
  • Optics Type and/or Coatings: Everbrite Coatings
$189.95
Baader Planetarium 1.25" T-2 Maxbright Mirror Diagonal

Baader Planetarium T-2 Maxbright 1.25" Mirror Diagonal - MAX-1

SKU: BAD-MAX-1
  • Diagonal Type: Mirror Diagonal
  • Diagonal Size - Eyepiece Side: 1.25" Barrel
  • Diagonal Size - Telescope Side: 1.25" Barrel
  • Optics Type and/or Coatings: Maxbright Coatings
$249.00
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
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$319.00
William Optics 1.25" Dielectric Diagonal with Carbon Fiber Side Plates

William Optics 1.25" Dielectric Diagonal W/ Carbon Fiber Plates - D-125D-C-DB

SKU: WYO-D-125D-C-DB
  • Diagonal Type: Mirror Diagonal
  • Diagonal Size - Eyepiece Side: 1.25" Barrel
  • Diagonal Size - Telescope Side: 1.25" Barrel
  • Optics Type and/or Coatings: Dielectric Coatings
$95.00
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
iOptron 1.25" 45º Erect Prism Diagonal

iOptron 45º Erect Prism Diagonal - TDE100

SKU: IOP-TDE100
  • Diagonal Type: Prism Diagonal
  • Diagonal Size - Eyepiece Side: 1.25" Barrel
  • Diagonal Size - Telescope Side: 1.25" Barrel
$25.00
Baader Planetarium T2 90º Prism Star Diagonal with 1.25" Nosepiece and 1.25" Eyepiece Holder

Baader T-2 90º Prism Star Diagonal with 1.25" Nosepiece & Eyepiece Holder - PRISM-1

SKU: BAD-PRISM-1
  • Diagonal Type: Prism Diagonal
  • Diagonal Size - Eyepiece Side: 1.25" Barrel
  • Diagonal Size - Telescope Side: 1.25" Barrel
  • Optics Type and/or Coatings: 7-Layer Multi-Coating
$169.00
TeleVue 90º Enhanced Diagonal - 1.25"

Tele Vue 90º Enhanced Aluminum Diagonal - 1.25" - DSC-0125

SKU: TLV-DSC-0125
  • Diagonal Type: Mirror Diagonal
  • Diagonal Size - Eyepiece Side: 1.25" Barrel
  • Diagonal Size - Telescope Side: 1.25" Barrel
  • Optics Type and/or Coatings: Enhanced Aluminum Coatings
$132.00
Takahashi 1.25" Prism Diagonal

Takahashi 1.25" Prism Diagonal - TKA00547

SKU: TAK-TKA00547
  • Diagonal Type: Prism Diagonal
  • Diagonal Size - Eyepiece Side: 1.25" Barrel
  • Diagonal Size - Telescope Side: 1.25" Barrel
$147.00
iOptron 1.25" Dielectric Mirror Star Diagonal

iOptron 1.25" Dielectric Mirror Star Diagonal - 6231

SKU: IOP-6231
  • Diagonal Type: Mirror Diagonal
  • Diagonal Size - Eyepiece Side: 1.25" Barrel
  • Diagonal Size - Telescope Side: 1.25" Barrel
  • Optics Type and/or Coatings: Dielectric Coatings
$79.00
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

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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