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Building an 8" Closed Tube Reflector

Construction Pictures
Finishing End Cap and Fan

The mirror cell, end cap and exhaust fan are all one integrated assembly.

This is the end cap and cell bottom plate. It has been painted and is ready for assembly. The collimation bolts have been inserted from the back. Each bolt will get a washer, two belleville washer springs and another washer. I will provide part numbers and references from McMaster-Carr for these parts.  To the right we see the tip-tilt plate fitted and the collimation screws socked down.

The mirror is placed face down on protective material and three pieces of tape placed as shown to provide a stabile base. The mounting plug is visible and will receive the nylon mounting bolt and belleville washers seen below.

At the right the cell has been placed over the mirror and the washers and springs place over the mounting hole.

The nylon threaded rod and nut are screwed down until the nut takes up a bit on the belleville washer - that's it! Mirror mounted.

Fan mounting plate and fan are seen here. The fan is attached to a 2.1 mm, positive center, coaxial jack and will be mounted to the back of the plate using sponge rubber shock absorbers and silicone RTV.

Here is shown the soft sponge foam rubber mounts attached with silicone RTV. The fan is later attached on top of the shock absorbers.

Finished fan plate seen alone and attached to the end cap.

Final mirror and cell assembly.

Open end of tube and final attachment. You are now ready to collimate the telescope. The belleville washers have about 0.020" take up, if one corner is low you can put a regular washer under it to make up the difference. The collimation is remarkably stabile. In the metal version it really is almost permanent, but we await user reports.