…continuedFreeware from Sky & Telescope
In the Telescope Techniques department in the November 2000 issue of Sky & Telescope (PDF of article) Alan Adler described a revolutionary way of shaping telescope mirrors that circumvents much of the labor needed to grind a paraboloidal mirror. Adler took a spherical mirror and flexed it to produce a paraboloid. The article features a DOS program called Flex to simplify the process, which you can download here. Be sure to select "Save program to disk" when prompted, and unzip the file using an uncompressing utility, such as 7-zip or StuffIt Expander.