Hobbies And Interests
Things You'll Need
Instructions
Construction Steps
Spray paint the inside of the PVC tube with a matte black epoxy based paint ̵1; the duller, the better. Allow to dry and cure.
Determine the focal length of the telescope mirror you bought. The specifications will have come with the mirror. This will be the total distance from the center of the mirror to the upper end of the focuser tube. You will need to determine the fixed distance from the end of the focuser tube fully retracted to center of the secondary mirror mounted on the spider. Once you know this distance, subtract it from the focal length and you will know how far the distance must be from the primary mirror center to the secondary mirror center.
Mounting the spider/secondary mirror assembly at the open end of the tube. The spider legs will be evenly spaced around the inside of the tube opening an inch or two into the tube from the top edge. Drill holes for the screws or bolts that hold the legs in place. It is critical that each leg be exactly the same distance from the lip of the tube. Attach the legs and the spider will be placed properly.
Measure the distance that you determined in Step 1 was necessary between the secondary and primary mirrors using the the actual placement of the secondary mirror center as the starting point. Mark that distance down the tube. Add the thickness of the mirror and mirror cell/mount and add one more inch. Mark the tube and cut it off.
Mount the mirror/cell assembly inside the base of the tube, one inch from the lower lip. This should place the primary mirror at the correct distance from the secondary. Drill holes to match the mounting screws in the cell/mount assembly. Make sure the mounting holes are exactly the same distance from the top edge of the tube (in case you cut the bottom edge imperfectly).
Mark the point on the outside of the upper tube that is straight above the angled secondary mirror. Drill a hole for the focuser. Use a hole saw the same size as the focuser opening. A 3/4-inch focuser gets a 3/4-inch hole. A 1-inch focuser gets a 1-inch hole and so forth. Drill the hole directly above the center of the secondary mirror. Dismount both mirrors while you do this and remove them from the tube while making your hole.
Remount the spider/secondary mirror assembly and primary mirror. Mount the focuser assembly to the outside of the tube directly above the secondary mirror in a comfortable position for viewing.
Mount the spotting scope assembly to the upper end of the tube at a comfortable position for use. Usually 45 to 90 degrees opposite the focuser is usually about right for most scopes. Simply screw the base of the scope to the PVC tube with the screws supplied with the scope. Make sure the scope lines up parallel to the main tube.
Attach your telescope assembly to the telescope mount you have chosen following the manufacturer̵7;s instructions.
Collimate the mirror. This involves adjusting the collimation screws on the mirror cell/mount until, when you look through the focuser without an eyepiece mounted, you see your own eye in the center of the image. It takes some practice going back and forth between the focuser and the primary mirror mount till you get it right, but it̵7;s not difficult. Then, line up the spotting scope by focusing on a known large object and adjusting the set screws on the finder scope mount till the cross hairs strike the object in the same place as the center of the image in the telescope.