BUILD AN SCT BALANCE BAR

This project was built to fill a gap between the need for a balance bar for the telescope and shortage of funds which all hobbies seem to have. The use of easily available aluminum parts allows this project to be reproduced by most any handy individual. Aluminum is an easy metal to work with and except for one "cut" on the bar, this project was done with hand tools. A total cost for the project should be less then $30.

Parts list:

• One section of 1/2 inch aluminum U channel bar stock (Figure 1 below).
  
• Three 3/4 x 3/16 x 3.5 inch aluminum bar (size varies with design).
  
• 5/16 x 18 threaded rod about 6 inches long (varies with design).
  
• Misc. 1/16 inch thick teflon for bearing surfaces (optional).
  
• Surplus radio knob with brass insert (size varies with personal preference).
  
• 2 x 2 inch steel counter balances (varies with counter weight needed).
  
• Misc. small stainless steel bolts.
  
• Several drops of "lock tight" metal to metal "glue" (auto parts store).
  

The first step is to determine your current and future requirements for your counter balance system. The project described was only to counter balance a single 35mm camera on an older Celestron C8.

Safety first!
Always use eye protection and safety devices.

1. Collect needed items. Most will be available at a local hardware or building supply store.
2. Prepare your tools for the project. You will need a hack saw, drill and drill bits, thread taps, and misc screw drivers.
3. Cut one side of the U channel along the length of the bar so that it looks like figure 2 below. For this project, this was accomplished by mounting a metal cutting blade on a table saw.
4. Cut bend mark and drill 2 pieces of the 3/16 aluminum bar so that it looks like figure 3 below. The first holes will be for mounting to the OTA. These holes need to be drilled off center to allow for the attachment of the bar. Notice that on one end, the OTA holes will be on the outside of the bar attachment, while the other end the hole will be in the middle. The attachment hole on the older Celestron C8 SCT seem to be designed so that 3 screws will be used to attach this project. Please inspect your OTA, it may differ from the one in this project.
5. Cut the modified U bar stock to a length which will fit your OTA. The use of 45 degree angle allow for a nice look and less of a chance for personal injury from sharp edges.
6. Drill holes in the 3/16 aluminum bars to attach your modified U bar stock. Tap holes and attach the pieces with stainless steel bolts. You will likely need to shorten your bolts with a hack saw so that they do not protrude through the 3/16 bar and into your OTA.
7. You should now be able to attach your bar to the OTA. The use of furniture felt on the bottom of the 3/16 bar will allow you to attach the bar without fear of scratching your OTA. This little measure can improve resale value of your scope.
8. Prepare a third 3/16 bar with 3 holes. The center hole is to allow a threaded rod to be "lock tight" attached. The 2 other holes are used to attach a piece of teflon to facilitate smooth sliding of the counter balances. The teflon is optional. Tap the center hole, and attach the threaded rod DO NOT "lock tight" the rod yet.
9. Drill the hole of the radio knob through the plastic. Then tap the hole to fit the threaded rod you are using for the balance weights. Make a washer from teflon to go under the radio knob to facilitate smooth sliding. This teflon is optional.
10. Cut some steel plate stock to become counter weights. The size in this project was 2 x 2 x 1/4 inches. These are then drilled and tapped so that they can attach to the threaded rod.
11. Assemble the slide unit to the bar and carefully move the scope. Watch for points where things will hit. Determine how long the threaded rod should be for practical use, then cut it to length. Now "lock tight" the rod to the bar. Let stand to dry.

 Figure 1
  This is an end view of the "U" channel aluminum bar.

 Figure 2
 This is how the "U" channel should look after cutting.

 Figure 3
 3/16 bar bent to fit the OTA.

End view of the 2 modified "U" channels attached to 3/16 bar
forming a new channel for the slide to slide in.

Side view of 3/16 bar with the "U" channel attached.

 Layout of slide bar which fits inside the modified "U" channel.

Photo of the slide assembly, a single weight, radio knob and teflon washer.

Photos showing the slide bar assembly. Notice the brown furnature felt to protect the paint.
Notice too that the OTA required one mounting screw at the corrector (right photo)
and two mounting screws at the mirror end (left photo).

Photo showing the the completed assembly in action.