Eliminate reflections by screwing in the focuser:

Eliminate reflections with a screw in the focuser:

Some focusers use shiny screws that extend into the focuser tube to attach the rack rail. These create reflections during astrophotography and visual observation.

The anti-reflective paint from Astrogeräte Berger (http://www.astrogeraete.de/Antireflexfarbe.html) makes it easy and straightforward to blacken the screw.