Here's a superior Obsidian Lite 12.5" f/6.5 paraboloidal mirror on fine-annealed plate substrate at 0.68" thickness (5 lbs total).
Properly supported by a 6 or 9-point flotation mount, this mirror will provide exceptional performance and outstanding thermal tracking, with worst-case estimated Strehl around 0.988. The mirror is guaranteed to meet or exceed .07 (1/14th) wave PV wavefront accuracy. It features excellent polish, diffraction edge, figure of revolution, and smoothness. Diameter 1 (see full test on website for SN0401) is slightly better corrected than diameter 2 - this is not unusual for thin plate even using our whole-mirror methods.
The mirror comes with a signed certificate of optical quality and is fully guaranteed to satisfy completely in performance, given proper mounting, collimation, and diagonal quality. Price is $450, shipping of $15 to domestic US. It is brand new and uncoated, coating can be arranged during delivery and our website lists some recommended coaters.
Why go Lite?
Two words - performance, and performance.
The high precision built into our lightweight mirrors is fully exploited with a modern flotation mount. Light weight means never having to haul needless weight around.
Thermal performance is the second advantage - without fans, you can have a telescope that has negligible thermal equilibration time. That means that more of the time you'll be viewing with a fully accommodated mirror, which is the only time any mirror can deliver its true performance.
Obsidian Lite mirrors combine high performance levels with thinner substrates for unparalleled thermal performance. Available on either fine-annealed plate and Pyrex from 12:1 to 18:1 aspect ratios, we target the correction on these mirrors to a Strehl of 0.975 or better (<1/10th wave PV wavefront). All other production factors are the same as for our Standard line.
By loosening the correction and economizing on substrate, Lite mirrors represent an outstanding value in today's market. Documentation is by Foucault Couder mask test across two axes.
Please note that full correction specs are available on precision annealed Pyrex at Lite aspect ratios, but we don't have a name for that. Pricing is more like standard, but a premium on extreme aspect ratios may apply depending on fabrication difficulty.
Plate or Pyrex?
We manufacture high quality mirrors from both. Either substrate when well annealed will perform to theoretical limits. Pyrex has lower thermal distortion and is easier to produce to higher precision, but no mirror can be used unless thermally equilibriated. At that point the glass only serves to support the coating, and no optical difference exists for either substrate.
The main advantage of plate is cost - by producing high quality mirrors on plate we make the heavens more affordable.
Thanks for reading our wordy ad.
Obsidian Optics, Inc.