"Newtonian Mirrors made and certified in writing to be well within the most exacting, demanding Millies LaCroix tolerance - typically better than 1/12 wave on the wavefront - which is over three times as precise as the industry 1/4 wave standard." (See additional discussion under "Optical Talk" page at this website.) We use precision annealed Pyrex 7740 in the thickness' noted on the pricelist page. All blanks are assessed for unacceptable strain in the glass substrate. Blanks are fine ground and flat on the back side with a round bevel. Thin blanks are polished on the back side to improve their strength. The face bevel is polished to improve contrast. Fused silica (quartz) blanks are also available depending on availability. Please contact us for more information.For the most discriminating planetary observers who prefer a more portable high-performance telescope, we also offer 8", 10" or 12.5" aperture with an F/6 focal ratio, as the longer focal ratio possible in these sizes makes it possible to consistently achieve wavefront peak-to-valley ratings of less than 1/20th wave with our known process capability. And for the most discriminating CCD and Videographers who prefer a faster focal ratio we are proud to announce a line of faster, high quality focal ratio mirrors in all sizes. Currently 12.5" and 16" F/4 mirrors are being produced. Please see our mirrors in stock for availability. Our product includes not only a precise mirror that produces simply the best performance possible, but also a certification containing the tolerance, measurement accuracy, and process controls that make this performance possible. We can provide a complete explanation with the certification that will explain the methods used to calculate the numbers used and pertinent formulas. The data contained within the certification can be used to replicate conditions of test using attainable test methods, and thereby to confirm the accuracy of results provided. Testing and refiguring services are now available. For a test of your mirror, please send it properly wrapped and packed and insured via UPS with returned postage included. We handle coated mirrors properly. Don't worry about damage to the coating. Contact us if you're unsure about how to properly wrap it for shipment. The coating can also be assessed and it can then be sent out to be re-coated if you desire. For mirrors 16" diameter and under, please include $60.00 for this test. Mirrors 18" diameter and over include $80.00 for the test. The longest focal length our shop can accommodate is 112-inches. For your uncoated mirror, a complete test including a photograph of the strain test will be done for an additional fee of $10. If you choose to have your mirror refigured and your glass is strain-free, it is considered "your supplied glass". It will be fine ground on the back to our finish specifications and serialized as are all of our mirrors. The price for refiguring is our current listed new mirror price, for your given size less 35%. It will be polished complete and spherical, then figured to our premium specifications and given all the care and effort our regular premium mirrors receive. It will essentially be a new, quality Lightholder Mirror. |