PHD2

PHD2 Guiding is free, open-source autoguiding software designed to help astrophotographers keep telescope mounts accurately tracking a target during long exposures. It analyzes images from a guide camera to determine any drift and sends corrective commands to the mount to maintain precise pointing.

PHD2 is the successor to the original PHD Guiding project and is developed by a community of volunteers. It supports a wide range of hardware and control interfaces, reflecting its goal of accessibility for amateur astronomers while remaining adaptable to various setups.

The software works by capturing frames from a guide camera, identifying a guide star, and calculating the star’s centroid. Deviations from a reference position are translated into guide corrections for the mount’s right ascension and declination axes. It includes a Calibration routine to measure axis response, a Guiding Assistant to optimize exposure, aggressiveness, and other parameters, and an option to enable dithering to reduce fixed-pattern noise in stacked images. PHD2 can operate with single-star guiding or, depending on configuration, multi-star guiding.

Platform support and integration: PHD2 runs on Windows, macOS, and Linux, using ASCOM for Windows and INDI for cross-platform control. It supports a broad set of guide cameras and mounts through widely used drivers, and can be used standalone or integrated with other astronomy software and workflow tools.

Impact and status: The program is widely adopted in the amateur astronomy community for improving image quality in long-exposure astrophotography. Its open-source nature encourages community contributions and ongoing improvements, with regular updates reflecting new hardware support and features.