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Dielectric Mirror Diagonal for Astronomical Telescope with 1.25 inches Adapter

  • Excellent Quality Dielectric Diagonal; Mirror Star Diagonal - 99% Reflectivity?Provides a Comfortable 90 Degree View from your Refractor; Fits Standard 2" (50.8 mm) Diameter Focus Tubes; Use Both 2" (50.8 mm) and 1.25" (31.75 mm) Eyepieces
  • New 2" 90 deg 99% Dielectric Mirror Diagonal for Telescope With 1.25" adapter; full metal;has a 1/10th wave flat optical glass surface;solid aluminum housing;threaded to accept standard 2" filters;The 2" eyepiece holder uses a non-marring brass compression ring to secure your valuable eyepieces. The 1.25" adapter also has a non-marring brass compression ring
  • Both sizes of eyepieces may be used and are protected from dings and scratches that would result from a standard set-screw. This 2" diagonal works with any Refractor that accepts a 2" star diagonals. It can also be used with Schmidt-Cassegrain or Maksutov-Cassegrain with an optional 2 inch visual back (See below)
  • Dielectric diagonal is especially important;A standard aluminized diagonal has about 92% reflectance;And this decreases with time as the aluminum mirror surface ages
  • For the vast majority of the visible spectrum;the reflectance does not vary more than about 0.1% below 100%;And the dielectric surface does not age like aluminum;This combination leads to the equivalent of a little more light grasp compared to standard diagonals

If you paid for high performance coatings for your telescope, why lose 8% of your light using a standard diagonal

We list our dielectric coated diagonals at 99% reflectance, but this does not tell the complete story.
While the reflectance is at a little more than 99% for the deep violet and reds, the reflectance for a the rest of the spectrum is essentially 100%

100% Brand New and Never Used
High glossy finish appearance
Threads fit standard 1.25'' and 2'' filters
Excellent Quality Dielectric Diagonal
Provides a Comfortable 90 Degree View from your Refractor
Fits Standard 2" (50.8 mm) Diameter Focus Tubes
Can Use Both 50.8 mm and 31.75 mm Eyepieces
Has a non-marring brass compression ring to secure your valuable eyepieces
Material: Metal
Color: Black
Net Weight: 529g/18.67oz

Package Includes:
1 x 2" 90-deg Dielectric Mirror Diagonal
1 x 1.25" Dust Cover
1 x 2" Dust Cover


  • We offer FREE shipping on all orders!
  • We ship within Three business days of payment, usually sooner.
  • We use a selection of shipping services such as UPS, FedEx, USPS etc.
  • We only ship to the lower 48 states, no APO/FPO addresses or PO Boxes allowed.
  • Local pickups and combined shipping options are not provided at this time.


  • You can return a product for up to 30 days from the date you purchased it.
  • Any product you return must be in the same condition you received it and in the original packaging. Please keep the receipt.


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Filed under: Eyepieces & Accessories