Effect of black coating on the inside of a hobby telescope's tube? I was watching this (rather old) episode of The Making, where they show how a telescope is built in a factory. At 7:34, the cylindrical body of the telescope is shown to have a dark coating on the inside and the video explains that this prevents internal reflection of the light received from whatever you're observing.
I saw an interesting comment from Izumikawa Fukumi who asked if the telescope would become more accurate if they coated the inside with the blackest black in the world. How would such a dark coating affect the telescope's performance?
Telescopes have the inner part of the tube blackened to minimize scattered light reaching the eyepiece. Such scattered light reduces contrast, and hence reduces the ability to see very faint objects, or low contrast detail.  A complementary approach for refractor telescopes is to use baffles in the tube. The baffles form a physical barrier to scattered light.  However baffles are costly to make accurately and add to the weight of the telescope.
The more that scattered light is reduced, the better the performance.
Alternatives to super absorbing paint are to attach to the tube, either matt black velvet, or sand paper sprayed with matt black paint.