This past weekend, I finally got my astrophotography observatory in Chiefland, Florida (above) up and running so I would have a place to image deep sky objects in a somewhat permanent setup. After having a chance to use my Takahashi TSA 102 refractor telescope on a pier (left) a whole new world opened up for me. I could slew the scope from one celestial target to another and then view the objects with absolutely no vibration or shaking in the telescope, even at high magnification. What a difference. The pier in the observatory is a 6 inch square steel tube that is set 3 feet into the ground with a surrounding 24 inch square concrete pad, built to support a heavy telescope/telescope mount. That was my first experience using a pier as the base for a telescope instead of a tripod and it caused me to give some serious thought to using a pier on the telescope I will be using at home for observing, an 8 inch Celestron Nexstar 8 (right). The problem is that despite a concerted effort to find a pier adapter to mount the Nexstar 8 on a pier, I couldn't find anyone who manufactured one. Not to be deterred, I decided to fabricate my own.
In addition to the two square pieces of aluminum, I had the metal shop cut four pieces of 1 1/2" aluminum bar stock into 4" lengths to serve as spacers between the top and bottom plates . By having 4 inches of clearance between the top late and the bottom plate I gave myself enough space to bolt the adapter to the pier. Equally important, the space between the plates would make it easy to attach and remove the telescope from the pier by using socket cap screws through the underside of the top plate into the threads on the Nexstar's mounting plate. The plates and aluminum bar stock cost was less than $50. I picked up the necessary hardware at a local Ace Hardware - eight 1 1/2" long, 3/8" stainless beveled screws to attach the aluminum rods to the two bases and the three 1" long, 3/8" stainless socket cap screws - to build the pier adapter at a cost of $15. Now came the fun part.
Step one was drilling four 3/8" holes into the bottom plate (above, L). Although the image doesn't show it, I then used a countersink bit to create a "V" shaped bevel in each hole on the bottom of the plate so the beveled screws would be flush with the plate when inserted through the holes. Step two was drilling 5/16" holes through the center of each aluminum rod (left) and then threading the holes with a 3/8 NC tap (right) to accept the 3/8" screws. This is where the choice of aluminum stock was a blessing. Drilling and tapping thick aluminum is much easier than comparable steel stock.
Step three involved attaching the aluminum spacer bars to the bottom plate so I could make another template that would give me the location of bolt holes on the top plate (above).
After I finish the adapter I will be building a pier in the back yard and attaching the adapter to the pier. I'll probably use an 8" Sonotube filled with Sacrete and rebar rods for support. Threaded "L" rods inserted into the wet concrete will serve as the attachment method for the adapter to the pier. Stay tuned.