Piano wire supports are made of spring steel. They are very resistant to axial pressure but have a little give laterally. That's why they can perform their two functions: 1. Keeping the mirror in place without any shift in whichever direction. 2. Preventing astigmatism when the mirror moves axially on its cell while moving the telescope from horizon to zenith or vice versa. The picture to the left shows the "off the shelf parts" of a piano wire support. To attach the piece of wire to the nut, a small (1.5 mm diameter) hole has to be drilled at the center of the bolt. The same goes for the piece of aluminium. The aluminium is glued into the piece of brass tubing, forming a "house" for the piece of teflon.

To the left is a picture of an assembled piano wire support. To adjust the heigth the bolt (with the piano wire and piece of teflon on top of it) can be turned in and out of the coupling nut. The nut is used to lock the support when adjusted, by fastening it against the coupling nut. The coupling nut will be glued into a piece of wood, which in turn will be screwed against the braces in the lower (when pointing at the horizon) corners op the mirrorbox. The teflon must touch the mirror at the center of its width and point to the center of the mirror (which they do automatically when attached to the braces). Of course it's also possible to make more then two lateral supports. Frederic Gea, from whome I have the idea, uses three supports at 120 degrees. A link to his "piano wire page" is on my linkspage. In that case the corner braces cannot be used to attach the supports to.

Below is a photograph of the piano wire supports in my 20 inch scope. It's not a very good picture, but I think it makes clear how the supports are mounted in the mirrorbox, against the corner braces. In the picture, the telescope points to the horizon, so the weight of the whole mirror (48 lbs) rests on the two 1.5 mm thick piano wires. Here is a picture of one of the piano wire supports. Below the mirror the fan blowing over the mirror surface is shown.

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