Large Telescope Tube

The telescope is build in a Serrurier truss tube design. The mirror support is a very important point of a telescope. Our cell is made with a Lasalle-system which uses 24 points on the back side of the mirror that are all resting on small counter-weights on roller-bearings. The force of each point is optimized with FEM calculations. The residual surface error is less than 15nm. The lateral forces are on the mirror are also caught by Lasalle-counterweights. We removed a major error source now by moving the lateral supports in linear bearings. We found out, that otherwise, the mirror can be tilted by the lateral supports and decrease performance in pointing and tracking.

The field derotator is driven by means of DC-Servomotors. The derotator is driven by a large worm gear, is nearly back-lash free and the accuracy is better than 20" (less than 10 microns for the specified field diameter).

The cleaning of the mirror can be done with the mirror left inside the tube. All the side metal sheets can be removed so you will be able to have an easy access to the mirror. This method is to be preferred in relation to other methods because you will not need to adjust the optics after cleaning. For the removal of the optics the lower part of the tube can be unscrewed and the optic can be removed with belts and a pulley-block.