Glare Glare: Stray light reflected in the telescope which interferes with the light from the object of interest. A very common problem in newtonian telescopes is glare. An easy way to check a telescope for strong glare is to view a star near the moon, but with the moon just outside of the field of view. The light from the moon, shining on the inside of the tube wall, bounces around trying to get into the observers eye. This stray light brightens the whole field, reducing contrast. The same thing happens even when the telescope is pointed away from the moon - city lights, bright planets, and even fairly faint sky glow can get into places it shouldn't and reduce contrast. One way to reduce glare is to install baffles in the tube. If these baffles closely match the desired cone of incoming light, and are spaced properly, then most of the stray light coming from other directions will hit a baffle instead of finding it's way to the eyepiece. A rough, very flat black surface inside the tube walls will also help to soak up stray light. Note: Baffles which closely match the light cone can cause another problem - tube current eddies. See the Atmospheric Distortion section of this help file. Adding baffles to a telescope can sometimes improve image contrast enough to allow the observer to detect very faint details which could not be seen before. There are many ways to make baffles. Thin wooden or metal ones are the most accurate and professional. One simple suggestion is to use foam weatherstripping for sealing doors - available at any hardware store. The foam should have a rough surface to soak up light. Fortunately, this type of foam is less expensive than the higher density, slick type. The tape backing will not hold up under the temperature range a telescope is used in, so it should be glued in place. A couple coats of very flat black paint should be applied. The algorithm used by Newt to calculate the position and diameter of the baffles only works for the lower end of the telescope. Newt adds one baffle at the top, and one baffle on either side of the focuser. In actual practice, several baffles should be added above and below the focuser to create as much shadow as possible on the inside tube wall opposite the focuser.