I have always dreamed of a really large aperture mirror, who hasn't, but I had this mad thought earlier this week.
1 metre mirrors are out of the realms of amateur astronomy, but maybe they aren't
Here's the mad idea.
Basically you make a box that is air tight except for a circular hole the size of the aperture you wish to have on one surface, scale the box appropriate to the size of aperture you wish to have.
Inside you mount a vacuum pump and an associated controller to ensure that the vacuum generated remains constant and drill a hole to accept a one way valve to allow the pump to remove air from the box.
Then across the hole you have created fix a mylar sheet in such a way that it forms an airtight barrier.
Now you simply start the pump and the mylar sheet will deform always keeping a perfect parabola.
Now obviously the properties of the mylar sheet (how much it can be stretched without tearing), will determine the maximum or minimum focal length that can be formed or used.
But the basic principal is there. As long as the vacuum does not fail. and remains constant, for a given pressure a specific focal length will be formed.
I have tried this out in a very rough fashion. Basically a plywood box I put together, a vacuum cleaner, and a piece of mylar, and in principal the idea works.
I would imagine the key to the whole thing would be keeping the pressure in the vacuum chamber constant and accurate.
So the question is, has anyone tried something similar?
I have search the web but have not found anything similar being used as a telescope mirror, but have found similar setups being used for solar cookers and reflectors.
Not being an engineer or having any great experience of using vacuum pumps or being able to control the pressure, is this a non starter.
I amm tempted to try develop this further just for the hell of it, but scientific grade vacuum pumps arent cheap but still many many times cheaper than a large aperture mirror.
I have no idea whatsoever if it is even possible to keep a vacuum at the pressure that might be required accurately.
Looking forward to feed back, even if it is negative. If you can see a fatal flaw let me know.
Edited by efanton, 10 January 2020 - 07:23 PM.