![]() A Strehl ratio of 0.8 is good, 0.9 is excellent, 0.95 or better is outstanding. The best opticians now use the Strehl ratio for specifying the quality of primary mirrors. The mirrors are frequently tested for accuracy of overall figure as well as for the smoothness of the surface.Īll our Primary Mirrors are guaranteed to a Strehl Ratio of 0.90 or better. All our primary mirrors are precision made and finished with hand figuring to a perfect parabola. We have a complete in-house production facility. Reflectivity and quality of aluminisation and protective coating.Īt Aperture Telescopes, we offer Parabolic Primary Mirrors in diameters of:Īll proudly Made in India, right here at our optics shop at Manesar, Gurgaon.Quality of reflecting surface, accurately parabolised, smoothness of micro surface,.The main considerations for purchasing a Primary Mirror are as follows: The performance of a telescope is mainly dependant on the quality of its Primary Mirror. The Primary Mirror is also known as the Objective and is the heart of a good telescope. Superior Quality (SQ) Mirrors are up to l /20 (please specify when requesting a quote).The ‘Primary Mirror’ is the principal light-gathering surface of a reflecting telescope. High Quality (Q) Mirrors are l /8 from 12" focal length and longer. Stand-alone configuration OAPs are manufactured directly as off-axis segments.Ĥ. Focus Position of the OAP is oriented in the mount at 9 o'clock unless otherwise specified.ģ. Surface Accuracy: Specified over 90% of the clear aperture area (Test Wavelength 0.6328 microns)Ģ. Off-Axis Distance: +/-0.02" (standard configuration), +/- 0.125" (stand-alone configuration)Įdge Thickness: +/-0.05" (12" focal length or less), +/-0.10" (18" focal length or greater) Using the Chart as a Guide When Ordering Precision Mirrors and Mounts:Ĥ0 = 40 inch parabolic or vertex focal lengthĠ15 = 1.5 inch off-axis distance - specified along perpendicular from optical axis to inner edge of mirror Your SORL representative is always available to assist you with any clocking orientation questions you may have. Other orientations are possible, but may impact your final cost. NOTE: Please include the clocking orientation on your order. This is the position at which the mirror was fabricated and tested. Using the mirror at this correct rotational position will assure optimum wavefront performance. SORL Mounts identify the clocking orientation of your OAP, which specifies the OAP focus position and dictates location of the Reference Flat. Optical Coatings: May be selected from a variety of evaporated metals and dielectric materials for optimal performance in the wavelength region, optical power level, and environment of intended operation.ĪlSiO, our standard, is the most durable coating and has high reflectivity from Visible through the IR.Įnhanced Silver is better for higher power and has higher average reflectivity from Visible through the IR. Surface Quality or Finish: A measure of the optical polish, specified by "scratch/dig" values denoting surface imperfections, as defined by Military Specifications, MIL-0-1383. Due to reflection at the surface, the wavefront error is twice the surface error.Ĩ. Surface Accuracy- Deviation from perfect paraboloidal shape, specified as "peak-to-peak" (peak-to-valley) value in fractions of the interferometric test wavelength 0.6328 microns. Standard OAPs sectioned from a larger diameter parent will be thicker.ħ. For stand-alone mirrors, this is approximately correct. ![]() Edge Thickness (ET): To insure structural stability, a mirror will typically be made from a blank having a 6:1 diameter-to-thickness ratio. Clear Aperture (CA): The optically qualified region of the mirror surface.Ħ. Outer Diameter (OD): Outer mirror diameter measurement compatible with physical requirements.ĥ. Off-Axis Distance (OAD): Specified along a perpendicular from optical axis to inner edge of mirror.Ĥ. Only the focal length, measured along optical axis from vertex to focus position, need be specified.ģ. Focal Length (FL): True Parabolic or Vertex Focal Length, and off-axis Apparent Focal Length (AFL), should be considered. Alternatives include Fused Silica, ULE glasses, conventional metals, and light weighted substrates.Ģ. Substrate Material: Zero thermal-expansion ceramic (Zerodur or its equivalent) is the most stable and is our standard. When specifying an OAP, consider the following items:ġ.
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