I’ve built an electronic automatic focuser (EAF) for my Tamron 80 to 210 mm telephoto (zoom) lens for automated and precise focusing. The focuser was built with a stepper motor, an A4988 stepper motor driver, an Arduino Uno, and a repurposed azimuth adjustment mechanism of an old Vixen mount.
Vixen’s alt-az mount azimuth lock mechanism happens to be wide enough to fit a telephoto lens. It allows fine movement using the fine adjustment knob attached to a stepper motor with 60:16 pulley and belt system. It features a clutch mechanism that allows for manual focusing. The lens and the camera are held in place with mounting rings from an old 80 mm Vixen refractor. An aluminum baseplate is used to mount together as a unit the lens, camera, focuser, finder scope, and guide scope. The controller for the focuser was housed in a project box. A dovetail bar connects the whole assembly to the telescope mount.
I have tested the focuser on several imaging runs now and it appears to be working fine, especially with wide-field targets such as the Lagoon and Veil Nebula. To watch a video showing the microfocuser in action, click here.
DIY Electronic Automatic Focuser (EAF) | Refractor
DIY Electronic Automatic Focuser (EAF) | Reflector
Night Sky in Focus © Anthony Urbano | Bacoor, Philippines