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Is it possible to 3D print a mirror with todays available materials?

If so, would there be a reduction in image quality?

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If you can print a thermally stable material, the stairsteps may be unacceptable, but you can be very close to the desired contour. It would be a very good start for some polishing. – Ross Millikan Aug 10 '14 at 4:16

The highest resolution 3d printers I know of are around 1600dpi, which is a resolution of about 15$\mu m$. Telescope mirrors have to be smooth to fractions of a wavelength of light, so the resolution of current printers is nowhere near good enough.

Whether 3D printers could one day be good enough is a different question, but given that the improvement in resolution required is at least a factor of 1,000 I think it's not likely because 3D printers are designed to address quick manufacture rather than precision manufacture. In any case, making mirrors is a well established procedure. The difficulty is making them large, and it's not obvious how 3D printers would help with this.

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Active Optics telescopes which actually build the discs with small pieces. Their main problem is building small parts with accuracy. If we could just increase the resolution a bit, we would hit two revolutions at once. Don't you agree? – Cheeku Aug 4 '14 at 12:58
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Also, it is my understanding that 3D printers do not make smooth curved surfaces no matter their resolution. Such surfaces require extensive "finishing", which is what you currently have to do to homemade telescope mirrors anyway. So no gain at all there. – RBarryYoung Aug 4 '14 at 13:03
    
@cheeku no, each mirror's surface must be uniform to better than a wavelength. Now, for comparison, once a mirror is polished to the necessary smoothness, it's may be given a multilayer antireflective (AR) coating. You could look up vapor-deposition methods to see how evenly such coatings can be applied (although this is not a way to get macro-thickness "3D" coatings). – Carl Witthoft Aug 4 '14 at 13:16
    
@CarlWitthoft Yeah, I agree to that. My comment was directed to the last sentence of the answer, "...difficulty is making them large..." My bottom line: smoothness, yes. Size, not really. – Cheeku Aug 4 '14 at 18:13

The answer is "Yes" but not the way you might expect. It is possible to construct a telescope mirror from rotating liquid metal.Mercury used to be used but something like Gallium is safer and better.

So print a cradle for it, put in the Gallium, raise the equipment past the melting point (about 30 degC), spin gently to get a parabolic surface, and then cool.

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Can't be done, yet. But don't expect 3d printing to stand still, it's only recently been born, wait till it starts walking, and running! My hope was that there could be a vacuum process that was usable in just enough vacuum to form a perfect mirror shape over a perfect mirror mold of some kind, then start the vapor deposition on the cheap, lightweight material that was drawn into the perfect mirror mold. Maybe you could make a lot of them before the mirror was harmed. Maybe a cousin of mylar. Large cheap mirrors would do wonders for science and astronomy, and people.

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Yep! Can just imagine printing out my own 24" mirror for a big reflector at home lol :D – Baconbeastnz Aug 10 '14 at 3:52

protected by Qmechanic Feb 3 at 13:02

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