Baader Turbo Film is highly precise protective film used as the base for AstroSolar safety film and is available in sheet form for DIY construction. This is not cheap Mylar, but a monomer film that Baader have selected after trying over 200 different substrates on their Zeiss autocollimator. This particular film has been used as an optical membrane in nuclear and particle physics experiments by prominent German science institutes, and has been further refined by a proprietary annealing process.
The result of these efforts is a perfectly homogenous film that performs equal to a 1/10 wave plane parallel optical window, with the lowest wedge error of any existing optical window.
Baader Turbo Film protects your valuable optics from dust and humidity, plus it greatly reduces air currents, all without reducing the optical quality of your telescope.
WARNING: While it is made from the base substrate used in AstroSolar film, Baader Turbo Film is NOT suitable for solar viewing or imaging.