Orion Optics UK elliptical secondary - 75 mm minor axis - 97% reflectivity

Highly reflective Secondary Mirrors for Newtonians

Newtonian primaries of ORION Optics UK belong to the best mirrors on the market. Also the secondaries play in the same quality league.

Accuracy: The surface of the secondaries has a roughness of 1/10 wave RMS or better.

The 97% HILUX coating: a true highlight - you gain substantially more light at the same aperture. Normal mirrors have reflectivities of about 90%. 10% of the light is lost, while at the Orion mirrors only 3% are not reflected. The object appears significantly brighter and the exposure times for photography are reduced.

For the same performance, a coating has to be 30% thinner if applied to a Newtonian secondary instead of a primary, as the light path is lengthened by the inclined light incidence. This is taken into account when the Hilux coating is applied.

The required size: It results from the diameter of the main mirror, its distance to the secondary mirror and the image field to be illuminated. The data can be determined graphically or by calculation, for example using a computer program.

The surfaces of mirrors - Information from Orion UK

Manufacturing precision optical surfaces, (in this category we include both mirrors and corrector lenses), involves many specialised procedures to achieve the high degree of optical precision, some of which occasionally leave surface blemishes on the optic (mirror and/or lens).

If there are a few sleeks or scratches on the optics’ surface they in no way effect the performance of the lens or mirror either visually or photographically and cannot be considered as an acceptable reason for any complaint. Small pits are occasionally visible due to processing in the polishing and figuring process, these again cannot be accepted as reason for complaint. We endeavour to have blemish free surfaces but cannot guarantee such. Accordingly, we have set our cosmetic surface finish at a high standard production tolerance as is practical. We apply an optics industry standard to our surfaces of 80/50 scratch dig which is a measure of an acceptable level of surface blemishes per optic is acceptable.