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Alexander Telescope Construction

Cylindrical Feed Horn

Cone Assembly

Start out by cutting the Shark Bite tubing. You will need (4) 23 ½ inch pieces to form the hoop and (4) 24 1/8 inch pieces to form the sides of the cone shape. (Tip: The tubing can be very challenging to cut. Avoid applying too much pressure towards any body part because the tubing tends to snap all at once rather than the smooth release commonly expected.)

To form the hoop, take the (4) 23 ½ inch pieces and (4) PVC Tees and attach them together to create a circle. Note you may have to bend the pipe to make it more pliable to assemble. *

Before super gluing the ends of the pipe into measure the diameter of the circle, it should be around 30 inches. Make sure all the PVC Tee’s are facing the same direction. *

Next, it’s time to attach the other (4) 24 1/8 inch pieces to the bottom side of the PVC Tees on your hoop.

Now here comes the tricky part to finish the whole structure of the cone. Take the last (4) PVC tees and attach them to the cone shape stove pipe. When we built ours, we realized it was harder than we thought. We first superglued the PVC Tees equal distance apart then gently wrapped string up and across the PVC Tees alternating sides each time. Then after they were wrapped we tightly tied we hot glued the string to the PVC Tees for extra security.

Note: There are probably better ways to do it, so feel free to explore other options.

Since the basic structure of the cone is complete it’s time to cut the Reflective Roll Insulation into the correct shape. The dimensions of the cone to fit the circle’s circumference is located below. We found that the best way to mark where to cut is to tie string to the end of a marker, measure the string to the right diameter according to the center point, tape the sheet of insulation to the floor so it stays in place and carefully stretch the string from one side to the other side to mark the top of the cone. (Think of this method as acting like a giant protractor with a pointer) Note: Only cut the solid red lines. Before cutting the bottom tip off that sticks into the cone shaped stove pipe it is best to fit it to size, mark, then cut it off. Make sure to leave an inch over hang off the top so you can wrap it around the top of your feed horn.

Reflective Insulation

Reflective Insulation

After you finish cutting the Reflective Roll Insulation to the dimensions above have somebody help you hold it while the other person secures it with duct tape. Note: It’s okay if it overlaps if it fits the cone structure.

Place the shaped Reflective Roll Insulation into the cone structure. Make slits across the top of the Insulation to make it easier to fold over and tape down. Use the HVAC tape to secure it down. It is recommended to tape it vertically over the slits you made.

Next tape the bottom of the Reflective Roll Insulation into the inside of the cone shape stove pipe. Make sure you use the HVAC tape and not duct tape. And you will have successfully completed the feed horn.

Cylindrical Wave Guide

Stove pipe Diameter: 6in Length: 13in


Waveguide

Cut a piece of the cylindrical stove pipe that is 13 inches long, this will be your waveguide. Cover the bottom with a piece of sheet metal cut to fit in the inside of the stove pipe and tape to the sides of the walls of the waveguide with HVAC tape.

Note: You will want to cut the bottom circle a little smaller than the diameter of the waveguide to allow rainwater to escape and not damage your telescope.

Next you need to cut a ½” hole in your waveguide. This needs to be placed a quarter of the wave length away from the back of the stovepipe. This is the place for your probe to eventually sit.

You will also need to drill two smaller holes for where screws will eventually be placed on opposite corners of the N-connector. It is best to temporarily place your N-connector in the hole so you can mark where the screw holes need to be placed. These holes will be approximately ⅛”.

How to connect your Probe

Cut the copper wire to a length of 4.86 cm. The length of this probe is important for catching as many radio waves as possible!

Now we need to attach our copper wire probe to the N-connector. The list of material given gives you enough materials to do this twice, because it can be somewhat difficult to put this together correctly on the first try.

Start by placing the copper probe into the N-connector holder as shown below.

The following directions were given to us by Evan Smith who has also made a radio telescope before but modified to make our of a radio telescope.

Using a blowtorch (5-10 seconds) or a soldering iron (1-2 minutes), warm up the spot where the copper meets the N-connector as much as possible without melting the white insulation material. Once it is warm, melt solder onto the spot. Do your best to make sure the solder solidifies so that the probe is as straight as possible.

The location of your probe is vital because it is the largest contributor to sensitivity of your telescope! Listen carefully, drill a ½” hole through the waveguide halfway across the width-wise and 5.71cm from the back of the box. Be precise!!! You may have to make the ½” hole bigger by drilling at odd angles and twisting the drill around. Be careful not to lose your grip of the stovepipe (waveguide) if you attempt to do this beveling method. You should be able to secure the probe and its holder with two ⅛” screws and their bolts. The heads of the screws should be on the inside of the waveguide.

Now you will need to cut another hole in the bottom of your electrical box that will align with the hole on your waveguide. The hole in the electrical box should be ½” bigger on all sides so that it makes the following steps much easier.

Electrical box

Follow the diagram below to how to connect the mechanics inside your electrical box. Also take note that you will have to drill an extra hole in the side for the output radio signal (bottom side of the electrical box).

Electronics Assembly

Electronics Assembly

Electronics Box

Electronics Box

Base

    The base is made up of two 3ft sections of 2x4s and a square cut of plywood that is 27" in length and width.  To conjoin the 2x4s, you must mark the middle of each of them which would be at 18 inches.  What we want to have a space in the middle that is 1.5 inches, so you must measure out 3/4 of an inch from the 18 inch mark that you made earlier.  Use a skill saw to cut along these marks at a depth of 1.75 inches. Repeat this for the other piece od 2x4 and then join them together.  Now you will drill the 27" square of plywood to the "X" you just made with four screws. 
    Now we will begin making the legs of the telescope.  You will need a 8' 2x2 cut into four equal pieces all measuring lengths of 24".  For each of these pieces you must make a 15 degree cut on the ends so that they will form a triangle shape when set up.  After your cuts have been made, you can drill 1/2" holes into the opposite sides of the angled edges.  For support of the legs we will have cross pieces of 2x2 measuring 15" and 18.5".  They will connect to each pair of legs four inches up from the angled edge.

Putting It All Together : All parts now should be completed so it’s time to assemble. Place the waveguide into the box structure you made to hold it (attached to the threaded metal rod). Make sure the hole where the probe sits is aligned with the hole you cut out on top of the box. Next place the electrical box after completed onto the prospective area (align the holes in all three pieces) and secure it with screws. (Do not put screws through the waveguide!) Finally attach the stove pipe increaser on top of the waveguide and secure with the 7” hose clamp and many layers of duct tape. Your telescope is now complete. Now go test it out!

Telescope Base

Telescope Base