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Diagonals & Accessories

14 Items
William Optics 2" Dura Bright Dielectric SCT Diagonal

William Optics 2" Dura Bright Dielectric SCT Diagonal w/ Built-In Thermometer - D-DIG2D-C-DB-SCT

SKU: WYO-D-DIG2D-C-DB-SCT
  • Diagonal Type: Mirror Diagonal
  • 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: DuraBright Coatings
$149.00
William Optics 2" Dura Bright RotoLock Diagonal

William Optics 2" Durabright RotoLock Diagonal - D-DIG2D-ROTO-A2

SKU: WYO-D-DIG2D-ROTO-A2
  • Diagonal Type: Mirror Diagonal
  • 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: DuraBright Coatings
$198.00
William Optics SCT Adapter for Standard 2" Diagonal Gold

William Optics SCT Adapter for Standard 2" Diagonal - Gold - D-SCT-TA

SKU: WYO-D-SCT-TA-G
  • This adapter coverts the 2" push-in diagonal into an SCT diagonal.

  • All you have to do is replace the push-in nosepiece with this adapter.

  • WO has designed the adapter to have standard SCT female thread (2" & 24 TPI).

  • This SCT Adapter is anodized gold.
$39.00
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

William Optics Dura Bright 2" Carbon Dielectric Diagonal - D-DIG2D-C-DB-T

SKU: WYO-D-DIG2D-C-DB-T
  • Diagonal Type: Mirror Diagonal
  • 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: Dielectric Coatings
$139.00
$45.00

William Optics 1.25" RotoLock Adapter - Gold - F-ROTO-A2-125GDII

SKU: WYO-F-ROTO-A2-125GDII
  • This Rotolock adapter locks into the 2” opening of a WO Rotolock diagonal or focuser.
  • This is a steppingstone to attaching 1.25” barreled accessories.
  • Rotating the adapter ring will lock and unlock the inserted accessory into place.
  • Using this adapter will ensure that your accessory is centered.
$45.00
$45.00

William Optics Nosepiece for 2" Diagonal - WD-DIG2A

SKU: WYO-WD-DIG2A
  • This nosepiece converts a standard 2" SCT into a "push in" 2" diagonal.

  • To use this tool, replace the SCT adapter with the nosepiece.

  • Please note that this WO nosepiece will not work with 1.25" diagonals or 2" diagonals that have a built-in SCT mounting ring.

  • This is a great way to change your SCT diagonal to a "refractor type" diagonal.
$30.00
William Optics RotoLock Eyepiece Adapter & Visual Back for 2 WO Diagonals

William Optics RotoLock Upgrade for WO 2" Diagonals - D-ROTO-A2

SKU: WYO-D-ROTO-A2
  • This Rotolock upgrade uses a flange to connect to WO 2" Diagonals.

  • Rotating the ring with lock and unlock the accessories in place.

  • No thumbscrews are used, so users do not have to worry about marring.

  • William Optics' Rotolock upgrade comes with a plastic protective dust cover.
$89.00
William Optics SCT RotoLock Adapter & Visual Back - 1.25"

William Optics 1.25" SCT RotoLock Adapter & Visual Back - F-ROTO-A2-125-SCT-TA

SKU: WYO-F-ROTO-A2-125-SCT-TA
  • One side of this adapter has an SCT thread and the other has a standard 1.25" Rotolock visual back.

  • Simply rotating the adapter will unlock and lock the inserted accessory into place.

  • The design of the adapter will firmly hold and center the accessory.

  • William Optics has utilized internal ball bearings and detents in this design.
$79.00

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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