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8" Mirror Grinding
8" F6 Project

CONSTRUCTION DETAILS
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Another important component of a telescope is the mirror cell. It needs to be strong enough to support the mirror along with allowing air to flow. What I build is as simple as it gets. I don't know if I would use this design on anything bigger than a 8" or 10" mirror.

My 8" mirror being on the thin side of 7/8" thick needed more than 3 supports for the mirror. I used a program called Plop cell designer (Another utility found off the Internet), to help calculate the optimal number of support points, and position of for the mirror that I was going to use. What I used for the main cell was a 8" diameter 3/4" piece of plywood. Seen on the right is all my pre-marked holes, from ventilation to mirror support holes.

Here is all the vent holes cut, along with marker holes that will be used for the mirror supports. The actual supports will be silicone blobs. The marker holes will help bond the silicone to the wood. Three points around the mirror 120° apart will hold bolts that will be used for collimation These holes were drilled with the base attached so I could assure the holes would line up.

Instead of using springs I used a acorn nut as a pivot point against a fender washer. My design for this was borrowed from a article I seen in Sky-and-Telescope.

The whole mirror cell assembly would be held in the main tube by using #10 wood insert screws in the mirror cell base. Stainless steel bolts would be screwed into these.


The mirror cell would be painted with polyurethane first. After the polyurethane had dried the marker holes would be filled with silicone an built up to about a 1/4" high. I wanted the blobs to smash a bit to get good adhesion to the back of the mirror but not to much as to flatten them out. So I used 1/8" dial rods as temporary spacers to keep the mirror from smashing the silicone to much. After the silicone had cured (about 24 hours) the dial rods would be removed.

 


 
Programming by: Victor T. DeCristoforo
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Last Modified
October 17, 2009