Diagonal (90° / 90 Degree) Mirror Diagonal (Dielectric, 1.25″) for Telescope


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1.25″ Mirror Diagonal for Telescope

Now back in stock!  These extremely popular 1.25″ diagonals impressed with the quality metal build and fine machining.  Don’t put up with a terrible diagonal a minute longer!

One end goes into the Telescope – A 1.25″ eyepiece into the other.


  • •1.25″ 90 Degree Mirror Diagonal
    •Simple and Effective Design for improved viewing comfort
    •Blackened, strong stray light control
    •Superb reflectivity (99%+!)
    •Enhanced Dielectric Enhanced Aluminium Mirror
    •These are also multicoated for superb performance
    •Solid, well machined, factory collimated
    •These are genuinely shipped from our Brisbane warehouse – delivery within days!

Are these good?  Yes!  These mirror diagonals have had several dielectric coatings are added to both protect the surface, and also increase reflectance of the mirror by several percent over what can be achieved with only a protected SiO or MgF2 overcoat.  These are harder, and have superior reflectivity compared to enhanced silver mirrors.  Our customers love these.  We are confident you will too.

Why use a mirror diagonal over a prism diagonal?  Mirror diagonals are preferred for faster focal ratios – Prisms can introduce false color if used with fast focal ratios (e.g. f/4.5) and also introduce astigmatism.  While mirror diagonals have more scatter than prisms, mirrors tend to be brighter and sharper.  The mirror version also has a longer optical path, meaning that if you can’t rake out the focuser far enough to reach focus, a mirror diagonal may help.

Weight.12 kg
Dimensions15 × 13 × 10 cm

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