I have built a lightweight portable DIY star tracker for DSLRs. It uses a worm drive from an unused equatorial mount I have found in a local surplus shop. I used a geared stepper motor and an Arduino controller to spin the RA axis at the correct tracking rate to match the apparent movement of the sky. The setup was housed in a metal box that fits in a small camera bag. It mounts on a standard camera tripod. I have tested it to track accurately with a DSLR with an 80 mm to 210 mm telephoto lens.
Lightweight portable DIY star tracker for DSLRs
Night Sky in Focus © Anthony Urbano | Bacoor, Philippines