How to Make a Telescope Tube

Cut the two sonotubes to the length you need for your tube. Sonotubes can be bought from a concrete supplier in varying sizes. The tubes should be two inches larger in diameter than your primary mirror. Because sonotubes are somewhat irregular in diameter, you can often find two that are approximately the same size, but vary enough so that one will nest inside the other. Slide them together to form a single double-walled tube and cut them together to the length you want. This will be equal to or an inch or so greater than the focal length of the mirror, depending on how deeply you want to set the focuser. Screw the tubes together with 3 3/8 inch screws spaced evenly around the tube a half inch from either end of the tubes to make a single tube.

Gently peel away the plastic coat that is over the sonotube. If done carefully, it will come away in a single sheet without damaging the tube.

Spray paint the inside of the double tube first with white paint. Apply two coats. The bottom layer of white paint will help reflect outside heat away from the inside of the tube.

Apply matte black paint to the inside of the second tube. Apply three or more coats till the inside is thoroughly blackened. The black paint reduces stray light reflection which can muddy the image you see in your scope.

Paint the outside of the tube whatever color you choose, but do so in as few coats as possible. Paint is an insulator and the more coats you spray on, the more of an insulating effect it has. You want the outside of your tube to allow heat to radiate away from the inside of the tube during night viewing, so keep the outside paint thin.

Drill pilot holes for the primary and the secondary mirror mounts. Drill the holes exactly the size of the mounting screws that come with the mounts so the screws fit snugly and do not shift around. Following the mounting instructions exactly so the mounting screw holes will be exactly in place. The more accurate you place the pilot holes, the less collimating (alignment) your scope will require.

Drill the focuser hole with a hole saw according to the instructions that came with it. A .965 focuser will require a 7/8 inch hole saw. Use a 1-1/4 inch hole saw for a 1.25 inch focuser and a 2-inch hole saw for a 2-inch focuser. The hole, when cut properly will position the focuser assembly directly over the center of the secondary mirror. Your tube is now ready for you to mount the optics, collimate the mirrors and mount the tube on a sturdy telescope mount.