The Mirror Cell - III
..continued.
After the Hammerite is applied and has dried, rubber pads are glued in the correct positions. There are three pads on each of the floating supports and one on each of the brackets. The brackets are then loosely fitted to the cell body, as seen in the photograph. Rubber pads are also fitted to the bottom of the small alloy blocks that will hold the mirror in place.
The cell is now ready to take the mirror.
The mirror is lowered into the cell and the brackets are tightly pushed against the side of the mirror. Then the bolts that hold the brackets to the cell body are tightened. On the photograph you can see that the floating supports are now pressing against the back of the mirror. The small alloy blocks are then fitted and pressed down onto the bevelled edge of the mirror and tightened with the M4 bolts. The rubber pads on the blocks ensure a tight fit but prevent the mirror from being pinched. The latter can cause the mirror to deform enough to cause deterioration of the image.
The mirror is now secure and the cell can be fitted to the tailgate in the mirror box. Because of the mirror's bevelled edges, on which the retaining blocks press, none of the reflecting surface of the mirror is obscured by any part of the mirror cell. This can be seen in the photograph.
The mirror is now stored in its cell, in a closed box, in order to prevent dust from gathering on the mirror. Because the mirror is very sensitive to damage, it will only come out of its box to be finally fitted once the rest of the telescope is finished.
Total cost of the mirror cell: approximately £25
