What is diy-harmonic-equatorial-mount?

Leo-John233/DIY-Harmonic-Equatorial-Mount is an open-source hardware and software project for building a DIY harmonic equatorial mount for amateur astronomy. The description explains it was created because the author found the EQ3D equatorial mount too heavy to carry repeatedly, and commercial harmonic mounts cost too much relative to this DIY version's specifications. An equatorial mount is a type of telescope support that rotates around an axis aligned with Earth's rotation, allowing it to track stars smoothly as the sky moves. A harmonic drive reducer is a compact, high-ratio gear mechanism that provides precise, backlash-free motion, well suited for astronomy tracking. This design uses a GEM (German Equatorial Mount) configuration, driven by a 25-100 harmonic reducer combined with belt drive and a 42-stepper motor. The control system runs OnStep/OnStepX firmware on an ESP32-WROOM-32E microcontroller, which is the widely used open-source telescope controller platform. The electronics include a custom PCB with TMC series stepper motor drivers (compatible with both TMC2209 and TMC5160), Wi-Fi via an ESP07S module, Bluetooth, USB-B, and an integrated DS3231SN real-time clock chip. The mount connects to popular astronomy software including N.I.N.A., INDI, and ASCOM over Wi-Fi, Bluetooth, or USB. The README states the design achieves arc-second level RMS tracking accuracy without needing a counterweight for loads up to 20-25 kg. The estimated total build cost is approximately 2500 RMB, with machined parts under 1500 RMB. The README is written in Chinese. Software is licensed under GPL-3.0 and hardware under CERN-OHL-S v2.