Single Mode Fiber Coupling Tip Tilt Control for a Small Amateur Telescope

The current work presents a fiber coupling tip-tilt controller developed for a three-telescope experimental prototype of an Astronomical Fiber-Based Near-Infrared Heterodyne Interferometer. It is based on a commercial magneto-mechanical compact-disk laser-beam actuator on which the fiber-ferrule is mounted. The actuator is driven by a two-axis controller electronics board which was developed by us based on digital processing in a dsPIC33EP device with analog periphery, which reads the quad-photodiode signals amplified by 109, and drives the actuator with two high-current outputs. While this realizes the very fine and relatively fast (up to 100 Hz) fiber-position control in the telescope focus, as a basis to this, a relatively coarse and slow auto-guiding is given by an amateur guiding camera. During first optical bench testing we obtained an average coupled power increase of up to 50% under certain perturbations.