What is better than glass optical mirrors pastics?
I am new to astronomy, and I've been watching how expensive glass mirrors for large telescopes reflectors can be achieved.
I have a curious mirror quality can not be cast or stamped to say acrylic or polycarbonate plastic or other cheap, then polished and coated? Is there some property of plastic makes it less suitable for a telescope mirror?
It is probably not possible plastic mold with sufficient precision for use as a telescope mirror, because of the shape molded plastic shrinks as it cools. This would require polishing and mathematics, the plastic is too soft to polish with conventional methods.
Thermoplastic resins tend to slip under load, making long-term stability is a problem – save his mirror on the edge and may deform as a potato chip. This does not mean it could not be done – small precision lenses are routinely cast resin. But the driving force behind development of these technologies is the market of millions of tiny camera lenses. The telescope is a much smaller market, so that the incentive economic to develop the technology is weak, while technical difficulties are much greater.
Optical Telescopes Part 2
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