The 20-cm Schmidt-Cassegrain Telescope

The S–C telescope is a mechanical system with moving parts. As such, it is subject to vibrations induced by observers bumping the telescope, cars and trucks rumbling by nearby and even the workings of the telescope motors and accessories such as camera shutters. As the telescope vibrates it shifts its pointing angle slightly, resulting in the eyepiece image moving back and forth. The first rule in vibration reduction is that you can never totally eliminate vibrations. You can minimize them to such a low level that they no longer bother you but they will always be there.

Given that a telescope is ‘shaky’ there are several cures but first you must determine where the vibration originates. If you can grab the telescope at the eyepiece end, shake it gently and you hear the bearings rattling then moving parts of your telescope are too loosely coupled together. First look for loose screws securing the tube to the declination bearing plates and the fork arms to the base. Some makes and model types have adjustable bearings which can be tightened. Care should be exercised in tightening bearings since excessive tightness will make the telescope hard to move, especially in cold weather. Furthermore, overly tight bearings are merely high-efficiency transmitters of higher-frequency vibrations.

Next, look at the mount. If a tripod is used, ensure that all of the adjustment screws are tight.