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Telescope Diagonals & Diagonal Accessories

 

As the name suggests, mirror diagonals use a mirror to turn the telescopeโ€™s image at a 90ยฐ or 45ยฐ 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 be 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. Thatโ€™s why High Point Scientific also offers dielectric diagonals, like the popular Apertura 2โ€ Dielectric. 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, like the Celestron 1.25โ€, 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 check out some Amici prism diagonals, as these produce an upright image with a correct left-right view for low-powered eyepieces.