Brand new just figured 20" reflector telescope primary mirror. Thickness is 37mm, physical diameter 20-1/16", making for a relatively lightweight optic for its light gathering ability.
Focal length is 71.5" or F/3.57 This is ideal for a large visual Dobsonian, the moderately fast F/ratio allows for a compact scope to be built around it, and not requiring ladders to reach the eyepiece. For imaging, compare this to the Planewave CDK20 OTA at $32,000. This mirror has 3.6 times the photographic speed, and when fitted with a tunable Paracorr-2, will provide equivalent wide-field performance for a fraction of the cost.
As the Ronchigram shows, this mirror has an outstanding figure - well corrected, smooth, free of zoning or astigmatism. Star test is close to perfect, 1/10 wave P-V or better!
The mirror is as yet uncoated, and I can ship it directly to an aluminizing facility of your choice. Coating costs and shipping are responsibility of the buyer.
Extra international shipping charges to be paid by buyer.
Filed under: Eyepieces & Accessories