Blackening telescope tubes and telephoto lenses
Pimp your telescope with a pitch-black interior is a step that helps you increasing the instruments optical quality. Take a look from the side into the tube without velours and you will notice the reflecting surface. That stray light causes a decrease in contrast.
The self-adhesive Velours swallows stray light and gets rid of reflections. The tubes interior gets much darker and the image quality increases dramatically.
Is it necessary to do that for the entire tube?
the optimum is a completely coated tube wall. However a remarkable improvement shows up if you do the following:
— for Newtonians you just coat the focusers opposite part of the tube. This is where stray light has its biggest effect
— for a refractor, the front 2/3th of the tube are necessary as the last third is being covered by the focusers tube.
Blackening the Dew Shield
Also for dew shields, velour coating really makes sense. It not only helps increasing contrast, it also insulates the entire surface and therefore helps getting rid of dew problems.
Attaching the velours
The velours arrives well protected on a roll. When attaching the velours, please take care for a neat and clean working area that is free from dust. If you have any dust on the velours, you can easily use a lint brush to clean it.
For attaching the velours, you should also demount the optical elements. Take out all lens elements or mirrors.
Then use a sharp cutter to customize the film. Deduct the backside film and stick the velours to the inside tube wall.
Sometimes it makes sense to use smaller pieces to get rid of problems with bubbles or tricky parts inside the tube like screws or baffles.