TRO+Mirror+support+design

=**Mirror support design**=

The old TRO 30 inch mirror is 1 inch plate galss. The original mirror was very poor quality optically, but it still showed us objects in the sky like never before!

The original mirror was made during 1997 and was completed for first light in 1998. It was de-commissioned around 2001. After this we began to make the new TROK mirror.

In 2007 we had the idea of re-making the mirror. If it we could make it 'good' for low power, then it may be possible to make a 1M (40inch) mirror out of 1 inch plate glass.

The PLOP results below showed that it might be possible to re-make the old 30 inch mirror into an acceptable mirror using 54 point support. we would need to gring the back of the mirror flat (which was never done) and then re-grind the front.

PLOP shows around 27nM on the surface, which equates to 54nM on the wavefront.

The mirror support has now been completed. It is hybrid design of wiffle tree and bubble pack. Images of the support can be seen on the Making the mirror support page



One idea is not to make a 54 point support at all, but to make 6 large triangles arranged as an 18 point support would be, but to cover the triangles in 'large' bubble pack. The point loads on each bubble would be quite small and would not damage the bubble pack at all.

The test stand would be the basis for this. The first test stand in fact was not done in this way and was justa 3/4 inch plate of plywood covered in carpet and then a layer of large bubble pack. First tests at around 8 degrees altitude using the focult tester showed no perceptable astigmatism and only a small amount of altitude induced flexure. But it was at only 8 degrees from! The telescope wouldnever be used at that angle.

Testing and figuring would be done at a higher angle of around 15 degrees.



Dimensions for the beams that connect the triangles are given below. The ends of the beam dictate teh center of gravity of the sector of the mirror to be supported.

Each group of triangles at the end of the beam will be made into one 'large' triangle made from 18mm ply.

These triangles will be covered in large bubble pack to simulate many supports.



This will make construction of the mirror support easier than a 54 point support, but hopefully as good in performance if not better. Tests will prove this one way or the other. The simple test stand seems to work and this is even simpler than the mirror support design (see below). Admitedly this is only leaning back at 8 degrees at the moment, but will be leaning back at around 15 degrees during final figuring and testing.