My amateur telescope making page

The "Deep Space Scope" Design

Home | Astronomy | DS-3 |Truss construction

We now have the two ends of the telescope, and need to firmly connect them relative to each other.

• Create an optical bench. One easy way to do this is with a straight 2x6 board or (carefully) a 2x4 board. First, lay the board outside, on a table or bench, aimed at something a long way away. The top of a telephone pole will work for an object way off. Lay the primary mirror box on it's side onto the end of the board, aimed at the far away object. Then, somehow attach the secondary cage to the board, standing up. One way to do this is with wood clamps. Another would be with a few bricks. Move the focuser in/out until it is in the halfway position. Tighten/loosen the primary mirror mount until it is in a good firm position, not totally compressing the mirror mount springs.
• Place an eyepiece into the focuser. Now, move the primary and/or secondary back and forth until you have a good focus.
• Measure from the attachment points (brass rods) on the secondary to the top of the primary mirror box.  Add 1" for the depth of the truss holes in the mirror box.  Add an additional 1/2" for the distance between the top of the trusses and the holes in the trusses.  Also, add 1" of extra truss, since we only have a rough estimate of truss length at this point. This is an estimate of the distance from the top to the bottom of the trusses.
• Create the trusses. This is done using 6 pieces of aluminum tubing, 3/4" in diameter. When you buy this tubing, get the alloy that you can bend by pounding.  Using a hammer, flatten the tubing for a section about 4" long. Use a sander, grinder, etc to round the tops of the trusses. Drill a hole into each truss, 1/2" from the flat end, using an 3/16" diameter drill bit.
• Cut the trusses to the length as calculated above. Use a hack saw or tube cutter. If you use a hack saw, smooth the end using a sander.
• Clean up the trusses using a circular wire brush that goes into a drill.
• Use the trusses to build the telescope. Placing this contraption onto the 2x6 above, and aiming at a distant point, check out the length of the trusses.
• If necessary, cut the trusses until your eyepieces focus in the middle of the range of movement of the focuser.  Be sure to check all of your eyepieces before cutting the trusses.
  
• We now have a telescope that needs a mount.