Parabolic primaries for Newtonians - Ultra Grade - made by ORION UK - 300 mm f/4 - 1/10 Lambda

Newtonian primaries by ORION Optics UK belong to the best mirrors on the market. The English telescope manufacturer uses modern optical production techniques to produce mirrors with up to 600 mm diameter.

The precision of the optics

The manufacturer guarantees for each mirror a precision of at least 1/10 lambda PTV with a Strehl value better than 0.98. Proof is delivered by a Zygo test sheet including a graphical representation of the mirror surface and of course the values measured.

The result of this effort is a mirror of very high precision which enable high contrast for visual deep sky observation or photography. On the planet the theoretical diffraction limit will be reached and usually the limit is the Earth atmosphere rather than the mirror.

The 97 % HILUX coating

A real highlight - you gain about 1" in aperture when it comes to light collection power. Normal mirrors have only about 90 % reflectivity, so 10 % are lost while the HILUX coating loses only 3 %. The object is discernibly brighter and the exposure times for astrophotography are reduced.

The substrate

Low expansion PYREX of Corning - this material has an excellent thermal behaviour. PYREX blanks are very homogenous and they are used for a long time to make quality mirrors.

Fast cool-down

The low thermal expansion rate will be assisted by the low thickness of the mirror which enable a short cool-down period, typically about 50 % of the time for full thickness mirrors to reach thermal equilibrium. Hence the telescope is quicker ready to go for observation and photography.


Delivery contains:

• 12" f/4 Mirror 1/10 Lambda PTV
• Zygo Test Report