If you are already using PHD1, note that PHD2 installs separately from PHD1 so you can have both applications installed at once. Installing PHD2 will not affect your PHD1 installation or settings.

We also provide development snapshot builds containing the latest bug fixes and enhancements. These builds may not be as well tested as the general releases, but we would welcome your help testing them out.

Upgrading from an earlier version of PHD2? Just download and run the installer. There is no need to uninstall the older version first. If you do uninstall the older version, you will remove all your profiles and settings.

Note for Gemini/Gemini2 ASCOM users: PHD2 requires the latest Gemini ASCOM Driver, Version 1.0.56.0 or newer.

Looking for a Linux package? Patrick Chevalley has PHD2 Ubuntu packages hosted on Launchpad. If you are using another Linux distro, you can build PHD2 from source: Building PHD2 on Linux.