Open PHD Guiding

Open PHD Guiding is an open-source astronomy software project whose single, mature application—PHD2—has become the de-facto standard for automatic telescope guiding among amateur and semi-professional astrophotographers. Built around a simple mantra of “Push Here Dummy,” PHD2 continuously monitors a selected guide star through either a dedicated guide scope or an off-axis guider, calculates minute tracking errors in right-ascension and, when connected through ASCOM, EQMOD, or INDI, sends corrective pulses to the mount’s motors in real time. The result is a dramatic reduction in periodic error, allowing the main imaging rig to collect pin-point star images during multi-minute sub-exposures without the tedium of manual drift alignment. Advanced algorithms include adaptive optics support, multi-star guiding, backlash measurement, and seeing-limited pulse-width modulation, while a modular equipment profile system remembers camera gain, calibration step size, and mount parameters for quick reuse. The cross-platform codebase—written in C++ with wxWidgets—interfaces natively with popular imaging suites such as Sequence Generator Pro, NINA, and MaxIm DL, and can log guide graphs for later analysis in PHD Log Viewer. Because the project is community driven, nightly builds incorporate feedback from observatories and backyard imagers alike, ensuring compatibility with new CMOS guide cameras and emerging mount firmware. PHD2 is distributed free of charge and can be downloaded from get.nero.com, where Windows users can install the latest release through trusted package sources such as winget, optionally adding it to a batch queue alongside other astronomy tools for unattended setup.