Light absorbing paint Unwanted reflections inside a telescope or an accessory are a nuisance for visual observers as well as for astro imagers. The standard factory coatings of inner tube walls, eyepiece barrels, focuser tubes etc. often leave much to be desired. This is especially true for Newtonians, which are particularly susceptible to stray light entering the system. Some observers try to cure their instruments with either blackboard paint or felt lining. Both solutions have their drawbacks, as even matt- black blackboard paint still reflects a lot of light and felt tends to release lint which soils the optics. A better solution is the special light absorbing paint (Antireflexfarbe) produced and distributed by Astrogeraete Berger in Germany. The comparison below demonstrates how well the paint works. These are two images of the same focuser tube of a 110/440mm Skywatcher Newtonian against a bright light source. The left picture shows how much light is reflected by the inside of the barrel having the standard factory coating. The right picture shows the same barrel after its inside was painted twice with the special anti-reflection coating from Astrogeraete Berger. Both images were shot under identical conditions.
Focuser Barrel with Special Light Absorbing Coating