Celestron 1.25-Inch Twist-Lock Dielectric Star Diagonal

  • Enjoy better views through your telescope!
  • Premium Diagonal featuring Diffraction-Limited Optics.
  • 58 Layers of Dielectric Coatings over 99% Surface for Max Light Collection.
  • 90-degree Field of View.
  • Twist-lock Keeps the Eyepiece Centered on the Diagonal.
  • Accepts Standard Eyepieces, Barlow Lenses, Threaded Filters, and other Accessories with a 1.25-inch Barrel.
  • Sale
  • Regular price $175.95
  • $128.75
  • You save: $47.20 (26%)

More on the Way in 14 - 28 Business Days

Free Shipping
Add to Wishlist
Already have gear? Trade it in for cash or new equipment.

Accessories Added

OPT Telescope Expert

Want Help?

Ask Our Telescope Experts


Celestron 1.25-Inch Twist-Lock Dielectric Star Diagonal

This 1.25-inch Dielectric Mirror Star Diagonal ensures maximum light transmission without loss of optical quality. The Twist-Lock connection centers your eyepieces snugly. Upgrade your existing star diagonal to this premium one and enjoy brighter, sharper images without replacing your telescope!

Accessorize your Telescope for Optimum Viewing with the Dialectric Mirror Star Diagonal by Celestron

Revamped Optics

This star diagonal reflects the telescope's light path of 90 degrees to provide a more comfortable viewing angle.

In addition, the glass has 58 layers of dielectric coatings, which provide an over 99% reflective surface, delivering the maximum amount of light to the eyepiece.

Specialized Design

The Twist-Lock eyepiece holder secures any 1.25-inch eyepieces while keeping them centered in the diagonal, thus providing the best optomechanical alignment between the telescope and eyepiece.

Unlike traditional thumb screws, the twist-lock cannot scratch or engrave the barrel of your eyepieces. The twist-lock has an integrated 1.25-inch barrel stop that prevents 1.25-inch accessories with long barrels from damaging the mirror.

Detailed Mechanics

All the diagonal's mechanical parts are made of machined black anodized aluminum, except the twist-lock rings, which are orange anodized for visibility. The interior of the barrel is glare threaded and painted flat black to prevent glare. With all its features and these high-end finishes, the Celestron Dielectric Star Diagonal, 1.25-inch with Twist-Lock is one of the highest quality 1.25-inch star diagonals that Celestron has ever offered.

Standard Star Diagonals vs Dielectric Star Diagonal

The key specifications for a star diagonal are its reflectivity and its optical quality. This diagonal delivers top performance in both categories, with an over 99% reflective mirror and diffraction-limited optical quality. This ensures that virtually all the light collected by the telescope will reach the eyepiece without the diagonal affecting optical performance. Using a lower quality star diagonal can both dim the view and degrade optical quality. You can enjoy better views from your telescope by simply swapping out its diagonal for a premium one, like the Celestron Dielectric Star Diagonal.




Angle90 degree
Barrel InteriorGlare Threaded/ Flat Black paint
CoatingsDielectric/ 58 layers
Diagonal Barrel Size1.25"
Diagonal Included 1.25" Star Diagonal
Diagonal TypeMirror
Eyepiece Connection1.25" Twist_Lock
Free ShippingYes
Glass TypeBaK7
MaterialAluminum/ Black Anodized
Optical QualityDiffraction Limited
Weight7.5 oz