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.
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