All optics over 6 inches are carefully ground and slow polished on a Draper-Hindle type machine and each one is made entirely by me from start to finish. While some optics are produced in small batches, this is not a production line process. Every surface is carefully examined for pits and other surface defects and hand figured and tested until it meets or exceeds the specified level of accuracy. The Draper type machine was first developed by Dr. Henry Draper in the mid 1800s. It has the advantage of deriving most of its action from the stroke arm and not the rotating spindle. This naturally produces a highly regular surface of revolution and reduces the likelihood of circular zones in the surface and the introduction of astigmatism due to rapid rotation. The Draper machine is usually reserved for the production of larger optics, but I have designed and constructed one which handles work from 6" to 16".
Polishing performed in the classic method using only pitch polishers. The polishing process is slow and designed to produce a ripple-free and sleek-free surface suitable for high resolution astronomical work.
12.5" Test Flat
Where applicable, testing of all my optics is accomplished by the autocollimation method utilizing both 12.5" and 16.25" perforated flats. Of all the tests for parabolic mirrors, this is still my favorite. It is a true double pass test and the mirror surface is very accurately presented for examination at twice the accuracy of the center of curvature test. It is also a null test for paraboloids so no measuring of data and reduction is necessary. This test is also used in the testing of refractor objectives and Cassegrain and Ritchey-Chretien systems. One of the main advantages of this test is that it not only is a critical test for overall correction and zonal defects, but is scrupulous in revealing edge defects. The cause of most mirrors failing to perform well is an edge defect, the culprit usually being a very slight (but devastating in impact) broad turned down or rolled edge (an annulus of slightly greater radius) over the outer 5 to 10% of the diameter. This defect is often invisible in the common center of curvature test and is most easily observable in the star test as an inability of the mirror to produce rings inside of focus. One of the problems with center of curvature tests for single aspheric elements is that the entire surface can not be seen at once; thus, defects can not be seen in relation to the whole. Not only that, but the accuracy of any test falls off rapidly when the grating or knife edge or fringe pattern is not at the optimal position over the entire mirror surface and the fringe or shadow pattern is distorted by the changing radius of the conicoidal surface. The only truly dependable high accuracy tests in a production environment are null tests where the testing device can be optimized, and particularly ones that involve the concept of the double pass over the work piece and the multiplying and enhancement of errors.
Every attempt has been made to produce a high quality optic in which the buyer can feel confident and will let him or her see all that can be seen. These optics are not made in a third world shop by people who do not care or who know nothing of their intended use - and get paid by the (rapidly produced) piece. Every step of the way through the process, I think about the user and their desire to have the very best telescope possible. And the fact that my name is engraved on the work.