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Why is glass still the norm for amateur telescopes?
(lemmy.world)
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this post was submitted on 01 Jun 2025
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Why not use first surface reflection so that the optical properties are irrelevant. The primary large scope is a reflective Dobsonian mounted light bucket which is a Newtonian reflector on an azimuth base. I've had Smith and Oakley sunglasses with great durability for the metalized coatings that have lasted a decade and a half without issues. I've also had some cheap ones that wiped off with soapy water well over a decade ago.
If it wasn't so physically demanding I would absolutely try grinding my own mirror. The old school DIY technique is silvering. Surely a plasma sputtering coated polycarbonate is better than the old Brashear's or Rochelle salt silvered mirrors.
So what's the advantage of poly over glass here?
As an eyeglass wearer, the advantage is weight (comfort) and safety, with a tradeoff in clarity and for me, plastic is a bitch to keep clean and scratches much more easily.
None of this seems to matter for a telescope, so why bother?