Flocking a telescope by lining the inside of the tube with black flocking material is a way to absorb and get rid of unwanted reflections. Black paint works well for this.
The open tube of the Newtonian reflector is a desirable target for the unwanted stray light that may come from anywhere including street lights, the moon, and some bright stars. The inner surface of the telescope bounces off the light that further enters the focuser as well as the eyepiece. Ultimately, the background lightens up but the contrast of the image gets harmed.
It is important to find a reliable solution to this problem. Some of the best recommendations from experts are baffling of the telescope, attaching an extension of the tube, or flocking the telescope from inside using some light-absorbing material.
Baffling is considered the most valuable method but it requires more effort for calculations. In this context, flocking is believed to be the easiest solution for preserving the image.
The main idea behind flocking is to enhance the light absorption properties of the open tube’s inner surface while covering it using a special material. It ensures efficient absorption of the unwanted light instead of reflecting it. With the unbaffled tube, some quantity of the stray light will mostly enter the eyepiece; however, flocking can reduce the harm.
Usually, the telescopes are painted with black matte paint but this paint is not necessarily able to absorb light, mainly at oblique angles. You may also find some additional material options in the market to enhance the quality of flocking without hampering the quality of the image.
For applying the material on the telescope, it is first necessary to disassemble different parts of the telescope including secondary mirror assembly with the spider, main mirror cell assembly, finder holder, and focuser assembly. These instructions are more valuable for the Orion reflectors.
In order to take out the main mirror, it is first good to place the telescope upright while keeping the bottom part on the floor. After this, you need to unscrew all tiny screws that are located on the perimeter of the tube. Note that the mirror cell assembly must stay on the floor; therefore, it is good to find a helping person who could hold this assembly carefully during the operation. In the meanwhile, you can also clean or wash the main mirror safely.
The next task is to unscrew the four bolts used for the spider by hand. It is better to hold the secondary mirror holder in one of your hands, but make sure that the remaining parts do not fall down in this process. The focuser must be removed carefully by unscrewing the Philips screws. Note that you should not confuse these screws holding the focuser in the assembly with the collimation screws. After this, one should also remove the finder holder from OTA.
After disassembly, it is necessary to make some measurements to cut the required sheets or rolls of the material. Make sure that overlaps are minimum or it is even better to avoid them because flocking of paper cannot stick perfectly to itself. In case if the tube is larger, it is possible to simply roll the flocking paper into OTA.