My amateur telescope
The "Deep Space Scope"
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Two views of the secondary cage, or ring. Inset picture, below -
of the secondary "cell".
Next, we need to create the secondary cage. Depending on how you
it, weight in the secondary cage will either make your bearings larger,
force you into adding counter weight. See Bearings
below for details on balancing the telescope. There
some debate as to how far the eyepiece should be away from the
should you bring it as close as possible, minimizing the size of the
secondary, or should you use the focuser
of your baffling system. I choose to get the focuser as close to
secondary as possible, but choose a focuser that will keep my eyepieces
semi-baffled. Using NEWT, and taking vinyetting into account, I
chose an uncluttered
secondary ring diameter of 13". Add 1/4"
for "stuff" that we will have invading the light path, and the
ring needs to be 13 1/2" in diameter.
- Create the secondary ring with the
router. Outside cut first, 16" diameter. Inside cut next,
13 1/2" diameter.
- Make another small section of ring,
same as above. Cut out 3 sections, 3" long. Glue these to
the main ring, 120 degrees from each other. These sections hang
DOWN, and are for ring strength where we attach the spider.
- If necessary, sand the ring.
- Drill 3 holes, 3/16" diameter, 120
degrees apart, through the secondary ring above where you glued the
- Create the spider. This is (from
the top) a 1 1/2" washer with 7 holes, a 1" dowel 1" long with 4
holes, a 1 1/2" washer with 7 holes, a 1" washer with 1 hole, and a
dowel 2" long. The dowel should be a hard wood, such as
Oak. After cutting the 45 degree angle talked about in
the next sentence, this dowel has an oversize hole in it,
Working from the bottom back up we have a center shaft that is a 1/8"
brass threaded rod, 4 1/4" long. There is a small brass nut
and a pretty brass nut on the top. The bottom dowel has a 45
in it. We will use double sided sticky tape to attach the
secondary to this cut dowel. It then has a hole drilled through
the center that is about 1 1/2 times the size of the center
shaft. Drill ANOTHER hole part way through, right on top of the
first hole, from the 45 degree diagonal size. This needs to be
big enough that you can put a nut on the shaft, and have the nut sit
inside of this hole. We will pull up against this nut, holding
the whole thing together. Next up, we have a washer. Just
keep the center hole. Next up, we have 3 machine screws pushing
against this washer. These machine screws (Allen head screws) are 1/8"
diameter, 2" long. We columnate the secondary through these
three machine screws. Next up (after a quarter inch of air
space), is one of the two 1 1/2" washers. These washers have 7
holes drilled into them. The hole in the center holds the brass
threaded rod. Next out,
there are 3 holes that fit the machine screws. These are 120
degrees from each other, and are about 1/3" out from the center.
Next, as close to the edge as possible, we have 3 small holes that will
be used to attach the wires of the spider. See the picture to the right
if this isn't clear. Next up, we have three holes in the 1"
dowel, lined up with the holes in the 1 1/2" washer. Make these
holes one drill size smaller than the machine screws. That way, as
they go into the dowel, they will cut their threads into the wood. On
of it all is a spacer and then a brass nut.
- We need 3 threaded shafts that attach to the
shafts are threaded brass rods,
3/16" diameter, 2 1/2" long. Place these shafts on a piece of
drill a 1/16" hole in them, 1/8" from the end. Now, lets
Take a scrap piece of wood and drill a hole in it. Insert a long
threaded bolt through the spider center. Attach this setup to the scrap
of wood. Put a nail at the appropriate distance from
the center, about 6 3/8". Thread the wire between the spider center,
and back to the spider center. Be sure to include the threaded
shafts that will attach to the secondary ring. Wrap this wire
around itself three or four times for strength at the start and
finish. Clip off the excess.
- Attach the spider to the secondary
ring using three small nuts.
- Now, you have to guess (calculate)
where the center of the secondary mirror will be. This will be a
spot about 1.414 times the thickness of the mirror below the center of
the 45 degree cut on the dowel. We want to have the focuser aimed
at this spot.
- Make a 5 1/2" X 5 1/2" plywood mount
for the focuser. Mount your focuser in the location that will
have your eyepieces aimed at the imaginary spot mentioned above. This
should be near the middle of this piece of plywood. Then, glue
this piece to the secondary ring. To decide how far in towards the
middle of the ring to glue this
plate, you need to rack your focuser IN
all the way. You then want it to stick into the secondary
1/2". You may want to remove the focuser from the focuser plate before
plywood in place.
- Make a finder mount. Mine, for a
Quickfinder, is 2 1/2" X 2 3/4". On mine, I cut two vertical
grooves in the wood, which keeps the Quickfinder from turning around on
center screw. Mount the Quickfinder to the wood to make sure that it
works, then remove it
again. Glue this piece in place. You want the inside of the
wood to be flush with the INSIDE of the ring.
- Place the secondary mirror.
First, mark the center of the back of the mirror. Next, the
outline of the spider bottom (45 degree cut dowel) is marked on the
mirror. Attach the secondary with DUCK brand double sided
have had a secondary fall of it's holder using double sided tape.
In the future, I will use silicone glue to attach the
- Cool - we now have a Deep Space spider!