Amateur telescope makers can make glass mirrors accurate to 1/10 of the wavelength of light using very simple tools and processes. https://www.bbastrodesigns.c

Amateur telescope makers can make glass mirrors accurate to 1/10 of the wavelength of light using very simple tools and processes. https://www.bbastrodesigns.com/JoyOfMirrorMaking/Intro.html https://www.bbastrodesigns.com/JoyOfMirrorMaking/Intro.html