William Optics 1.25'' DURA-BRIGHT Dielectric Diagonal

William Optics 1.25" DURA-BRIGHT Dielectric Diagonal

  (17 Reviews)
✓ 2 year warranty


4x in stock shipped 1-2 working days

About this product

Model:  WOdielectric125
Part Number:  D-125D-C-DB

Offers a noticeable improvement in brightness, contrast and overall sharpness when compared to budget diagonals!

  • Dura-Bright thick mirror and dielectric mirror coatings for 99% reflectivity.
  • Precision 1/12 lambda surface accuracy.
  • 12mm-thick mirror substrate.
  • Threaded to accept 1.25" filters.
  • Compression ring to prevent barrels’ marring.
  • Internal safety stop prevents 1.25” barrels from hitting the mirror.

Introducing New 2014 model William Optics Dura-Bright diagonal - a dramatic step forward in the evolution of mirror diagonals! This 90° 1.25"mirror-type star diagonal has a Dura-Bright thick mirror and dielectric mirror coatings for 99% reflectivity which provides higher contrast and resolution during critical planetary, lunar and binary star observations.

Dura-Bright features 100% real carbon fiber side plates that add that touch of class your scope deserves.

The WO 1.25" Dura-Bright Diagonal was designed with several unique features to provide optimum performance and years of use.

Top-Notch Performance and brightness
• Dielectric coating allows 99% reflectivity.
• high precision 12mm thick mirror substrate flat for optimal image stability.
• Polished to 1/12th wave accuracy.
• Accurate design guarantees constant alignment. No further alignment needed.

Meticulous Craftsmanship
• Lock screw for eyepiece/adapter.
• Big, knurled thumbscrews are easy to turn even with gloves on.
• Threaded for 1.25" Filters.

Strikingly Beautiful
• Patented, elegant design.
• High-quality machining out of the best Aluminium.
• Internal antireflection baffling for highest contrast.
• Real Carbon Fibre side plates

Superbly Constructed
• Compression rings (both on diagonal and adapter) to prevent barrels from marring.
• Internal safety stop prevents 2" barrels from hitting the mirror.
• Designed for high-end scopes.


ReflectivityUltra High Dielectric 99% reflectivity.
MirrorPrecision 1/10 lambda surface with 12mm thickness mirror for best quality.
Accessories2"- 1.25" adapter with brass clamping ring,includes
MeasurementsInside diameter (48mm): threaded to fit a variety of filters.
WeightWeight : 210g

Customer reviews

Average Rating (17 Reviews):  
Write a Review and share your opinions!

Rating (max 5):  
Highly recommended.
11 July 2023  | 

Well constructed of metal and fibreglass and much brighter than the mainly plastic one that came with my telescope. Highly recommended, especially for anyone with a small-aperture telescope that needs all the light you can get. Super-fast dispatch and delivery from FLO.

Rating (max 5):  
Quality Item
02 September 2022  | 

Improved views through my 'classic' (!) 50 years old Prinz Astral 550 refractor. Recommended, as are FLO - great service.

Rating (max 5):  
Good value upgrade
09 August 2022  | 

Great optics and a clear upgrade from diagonal that came with scope. Feels very well made & substantial to last for years. Good value too.
Brilliant service, as always, from FLO.

Rating (max 5):  
Superb quality product
16 December 2021  | 

Bought to replace the cheap plastic diagonal that comes with most telescopes, a lot of beginner telescopes are dismissed as rubbish or useless but when you upgrade the diagonal and eyepieces its surprising how much it improves the experience.

This is a top premium product that will last and once purchased it can be used for future telescopes you buy.

Flo are fantastic, never had a bad experience with all the items I have bought, highly recommend.

Rating (max 5):  
This Transformed the Optics Path of my Skymax 127...
12 February 2021  | 

I bought a Skywatcher Skymax 127 a few weeks ago as my first OTA... I had studied many forums and watched hours of YouTube in deciding which scope to invest in... I decided on a MAK as itís great for planetary and Lunar viewing and also because itís a compact and Ďeasy to useí device. I was delighted with the performance of the scope but, inevitably, after using it a few times I wondered if I could make a few improvements by replacing some of the included Ďaccessoriesí. The supplied 25mm EP was quite good but the Skywatcher 10mm EP was horrible so, on the recommendation of FLO, I purchased a couple of BST eyepieces and discovered just how Ďaverageí the supplied EPs were! I also replaced the finder scope with a Baader Red Dot Finder and that also was a marked improvement. Then it occurred to me that the optics in the OTA were superb and also the new BST eyepiece was great but sat in between them was the Ďstockí Skywatcher Diagonal. After spending hours on forums (again) I was a little unclear as to whether buying a high-quality Diagonal would be worth the investment. In the end I decided to go for it, especially as the William Optics Diagonal had some great reviews for build quality and they are renowned for producing excellent optics.
I thought there might be some improvement but the difference, compared to the supplied Skywatcher item, is quite dramatic... looking at rooftops about a mile away itís a crystal clear image, where before it was ok but not really filling the full eyepiece with a quality image, itís also so much brighter...
Iíve yet to get a clear sky to try it out at night but itís just obvious that itís going to be a big improvement...
A few people on blogs are sceptical about this upgrade but for my Skymax 127, which has great optics in the tube, itís really allowing the OTA to do itís job... Brilliant!
If you have a Skymax 127 or you are considering buying one then fitting this diagonal is simply a no-brainer; it dramatically improves on an, already, good viewing experience and turns it into something quite special.
A lot of experienced people on various forums will claim that the improvement with a diagonal upgrade is small but on my Skymax 127 it has transformed what you see in the eyepiece...
I also now have an item that can be used with a high-end scope in the future... happy days...

Rating (max 5):  
William Optics 1.25" DURA-BRIGHT Dielectric Diagonal
04 December 2020  | 

Quality diagonal that delivers improved performance. Definite increase in brightness in the viewed image, and a good choice as an upgrade to the supplied star diagonal.

Rating (max 5):  
08 September 2020  | 

Not been used much due to cloudy skies locally. Excellent quality build as you would expect from this provider. Wonderful customer service as always from FLO, thanks all!

Rating (max 5):  
Very high quality
12 August 2020  | 

Exactly what you would expect from William Optics. Well designed and beautifully made.

Rating (max 5):  
First Class Service
05 May 2020  | 

First purchase from FLO, faultless transaction, fast and efficient. Just purchased more items. Highly recommended. Thank you.

Rating (max 5):  
William Optics 1.25" DURA-BRIGHT Dielectric Diagonal
07 February 2020  | 

I spent sometime reviewing a number of Diagonals to replace my standard issue 1.25 Celestron one, which came with my Nextstar SLT 6" SCT. Really in the end, I kind of narrowed it down to a Celestron "Twist-Lock", Tele-Vue or WO DURA-BRIGHT.

Well, I could have spent over £50 or more on the Tele-Vue, but when I ordered and received the WO DURA-BRIGHT (very nicely packed by FLO) I was very impressed!! Firstly, if you compare your Diagonal which was supplied with your Scope, (just look through it with your eyeball) with the DURA-BRIGHT, the difference is blatantly OBVIOUS. The Image is Bright and has More Contrast. The Build Quality is very good, and I had NO problems extracting my Celestron X-Cel LX eyepieces (some people mentioned issues with the compression ring, binding on the eyepiece undercut, with this type of locking system, which is used by several manufacturers by the way) all I can say is, I haven't found any Problem as such, just don't over tighten the locking Screw, and a very slight lift and wiggle, as you extract the eyepiece, if you ever find it necessary I suppose.).

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