Pier Fabrication
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We have been discussing various schemes for pier installation. However, a more immediate problem for many people is finding the material and accomplishing the machine work necessary for the pier itself. There are two parts to fabricate (1) the pier or column itself, and (2), the head or cap on the pier that will accommodate your telescope mount. You can have a local machine shop or blacksmith construct the pier and pier head; however, you may want to do more of the work yourself.

You will not need special tools or skills to construct a concrete pier by filling a pipe or other form with concrete. However, how do you even find the steel pipe for the pier? And what kinds of pipes are suitable for piers?

Steel pipe is used in plumbing as well as in building structures, and comes in a wide variety of diameters, wall thicknesses, and strengths. Various types of steel are available, including black iron, galvanized iron, and stainless steel. While we emphasize steel pipe, you may find aluminum or other materials entirely suitable.

A typical pipe for a pier might be 4-8 in. diameter, with a wall thickness of at least 1/4 in. The length needed will depend on how deep a hole you are willing to dig (say, 4 ft.), and the type of telescope and mounting. A typical above-ground pier height might be three feet for a ten inch Schmidt-Cassegrain. Thus a pipe length of about seven feet is what is needed. If you buy new pipe, you will probably have to buy a 20 foot minimum (and it weighs a lot, so transport is not trivial). The best alternative is to use second hand pipe. Good sources include junk yards, recycling businesses, scrap metal dealers, plumbers, and construction companies. We've seen great prices even for stainless pipe at our own favorite junk yard called - what else, "Reliable Junk" in Frederick, Md. Another excellent source or second hand pipe is a well drilling company: well casing is perfect for piers.

Figure 6.8 PIER STUCTURE WALL CONNECTION

The supplier of the pipe can often cut the pipe for you. However, be aware that they may cut it using a torch or other means that leaves a very rough edge. While this is fine for the lower end of the pipe, you will want a reasonably good edge at the top. You can also cut the pipe yourself with a hacksaw. Use good blades, and lots of oil. You will find that the cutting goes pretty quickly, e.g., a six inch pipe can be cut in about ten minutes.

The easiest way to remove bumps or to square off the end of the pipe (assuming you do not have a large lathe) is to grind the end with a hand-held angle grinder. This very useful power tool can be purchased for under $100, or rented by the hour. Use eye and ear protection, and watch the sparks fly! With care, you can grind the end of the pipe not only smooth, but square to the pipe axis to as good an accuracy as you can measure (better than 0.01 inch).

The second component of a pier is the head which holds the telescope mount. The head should include some leveling adjustments to compensate for a pier that is not quite vertical. The detailed head design will depend on the mounting requirements for your telescope mount. However, most mounts have central pivot bolt of about 1/2 in. diameter, and several additional bolts for use after the mount is aligned. If you have a tripod, you should use its head as the pattern for your pier head.

Now the challenge is to obtain the head material, shape it, drill mounting holes, and attaching it to the pier pipe. The same shops and businesses you visited for the pipe are good sources for the pier head material. A good material to use is steel plate, 1/2 inch thick, preferably in a circular shape an inch or so bigger than your pier pipe. Aluminum plate is also suitable. It is easier to work than steel, but not as rigid. Aluminum cannot be welded to steel, so your pier head attachment options are more limited. Whatever the material, you may find it much easier and cheaper to use a square plate, then using your grinder to round the corners. A standard drill press, 1/2 in. bit, and plenty of oil will give you the holes needed.

But how do you attach the head to the pier pipe? You might want to construct the head on a threaded coupling, and simply screw it onto the pipe. With good design, this approach is great, except that in most areas it is extremely difficult to find places that will thread pipe more than 3 to 4 inches in diameter.

Another option, and often the best solution, is to weld the head onto the pipe using either electric or gas welding. However, modifications will be difficult if you make a mistake, if the pier is not vertical, or if you later want to change the head or add a length of pipe to increase the pier height.

An alternative is to bolt the head to the pipe. There are a variety of methods. You can make simple L-brackets using 1x1/8 in. steel bar, and use 5/16 in. bolts to fasten the parts together. The L-brackets can be mounted on the outside of the pipe. However, you can make a neater job if you thread the holes in the L-bracket. Then you can put the brackets inside the pipe, and use bolts inserted from the outside. In both cases, oversize mounting holes will give you some latitude for leveling the head.

Figure 6.9 ALTERNATIVE PIER HEADS

If you can leave all or part of your pier pipe empty, you can run power wires up the inside, and have a very convenient power outlet on the pier. You can also drill and thread holes at later times so you can mount other things to the pier (e.g., eyepiece tray, electronics, bracket to hold telescope control, etc.). Finally, if you do have metal pier, you should remember to ground it to reduce any risk of shock, or of electronic interference.

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