You will only partially construct the Telescope Tube before going to the school. The telescope tube has an eyepiece holder, a spider (to hold the secondary mirror at the front end of the tube), a tailgate that holds the primary mirror at the back of the tube, and mounting blocks.

"Making the Spider Video" (.mov) Time (1:54)

Making the spider
You will need the following for preconstruction:

• a dowel with one end cut at a 45 degree angle and three grooves cut at equal (120 degree) intervals about 1/4" deep
• 3 cedar shims
• 3 pieces of leather scrap 1/2" square
• secondary mirror
• wood glue

1. Insert the thin end of the shim into the groove in the dowel and slide the shim back (so that the part in  the groove is getting progressively thicker) at an angle until the shim is snug. Mark the thin ends of the shims where they fit snugly into the grooves of the dowel.
    
2. Carefully cut the shim where you marked it. Insert it into the groove and glue it to the dowel. Repeat with the other two shims.
    
3. Arrange the three pieces of leather scrap in a triangle on the slant cut end of the dowel. Place them evenly between the grooves and glue in place. Let dry.

Glue the back of the mirror to the leather pads. Make sure the mirror is centered on the dowel. DO NOT REMOVE THE PROTECTIVE COVERING ON THE MIRROR! The mirror should be kept level while the glue dries so prop it up until the glue is set.

At this point the spider is too big for the sono tube. The shims need to be trimmed to fit inside the tube. The rest of the spider will be completed at the school. You will have the high school students determine how to center the spider in the sonotube. They will saw off the ends of the shims and glue the spider in place. It is VERY important that the spider be carefully centered in the tube. Have groups double check each other's work BEFORE cutting the shims. A common mistake is to measure the external diameter of the sonotube and cut the shims to fit that. This makes the shims too long but so close to the actual length needed that trimming is difficult. Make sure students measure the inside diameter of the sonotube and carefully measure the diameter of the spider. You could have them make a paper template with a compass. The high school students will also determine where the spider will go in the sonotube.

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Eyepiece Holder
You will need the following:

• cardboard tube
• 3" x 4" piece of masonite with 1.5" diameter hole cut in the center
• glue

1. Glue the cardboard tube to the masonite. Make sure the cardboard gets wet with glue.

2. The brass tube should fit snugly inside the cardboard tube and should slide back and forth fairly easily. If the fitting is too tight, remove some of the cardboard from the inside of the tube. If it is too loose, glue strips of cardboard inside the tube until you have a snug fit. You can also use a hose clamp to tighten the tube.

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"Tailgate" (.mov) Time (1:57)

Making the Tailgate

You will need the following:

• 8" square piece of plywood
• three 5/16" bolts
• cereal box cardboard
• three 1" square pieces of masonite
• compass
• saw
• socket wrench
• drill with 1/4" bit
• glue
• 2 thumbtacks

1. Find the center of the 8" square. Set the compass for the radius of the inside of the sonotube (not the radius of the mirror which is 6"). Draw a circle with the compass point at the center of the tailgate. Only the very corners of the wood will be touched by the pencil.
    
2. Saw off the corners of the tailgate at the pencil marks. Now the Tailgate should fit inside the telescope tube. (plane or sand to fit if necessary).
    
3. Draw a 4" diameter circle for the placement of the tailgate bolts.
    
4. Divide the circle into 6 equal segments and mark each of the six points.
    
5. Choose three of the six marks (every other one) for the equilateral triangle. We want two of the three marks to be towards the cut off corners.
    
6. Use a 1/4" drill bit and drill holes at the three corners of the triangle.
    
7. Screw in the tailgate bolts with a socket wrench. The bolts should be threaded right through the wood.
    
8. Turn the tailgate over. Cut a piece of thin cardboard (e.g., cereal box) into a triangle which will cover the protruding bolts. The cardboard should cover all three bolts where they come through the wood.
    
9. Apply glue to the center of the cardboard only and glue to the tailgate so the bolts are covered. Let the glue dry.
    
10. Apply glue to the top of cardboard at the three places where the bolts poke through the wood. Glue the squares of masonite to the cardboard directly over the bolts. The cardboard protects the mirror from the tailgate bolts if the telescope is dropped. This cardboard must be floppy (i.e., ends over bolts loose) so that the objective can be aligned.
     
11. Fix the position of the cardboard with two thumbtacks.
    
    Mark the top on outside of tailgate. The bottom of the tailgate is the side where the two bolts line up with the two sawed-off corners.

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