PHD2-DrPi is a fork of PHD2, the enhanced, second-generation version of the popular PHD guiding software from Stark Labs (OpenPHDGuiding). It starts from the base PHD2 source and adds support for guiding Alt/Az mounts with a field derotator, keeping the original equatorial behavior unchanged.
Starting from upstream PHD2, the following capabilities were added:
- Alt/Az mount geometry — selectable Equatorial / Alt-Az / Auto-detect (ASCOM
AlignmentMode), with Alt/Az-aware calibration and guide math (declination compensation neutralized, pier/parity guards, cos(altitude) azimuth-rate compensation, Az/Alt axis labels). - Drive-capable rotator — the rotator device can now be driven
(
MoveAbsolute/IsMoving/Halt/step size/reverse) for ASCOM (IRotatorV3) and the built-in simulator, in addition to the original read-only angle reporting. - Field derotation while guiding — a derotation controller drives the rotator to cancel field rotation in lockstep with guiding, on the secondary worker thread so it never blocks exposures or mount corrections.
- Three field-rotation determination methods:
- Analytic — parallactic-angle rate from the mount pointing, site latitude and time.
- Image (guide stars) — rotation of the guider's multi-star constellation.
- Image (full-frame) — an independent, constellation-independent estimator that detects its own star catalog across the whole frame on a dedicated worker thread, matches it with a RANSAC rigid-transform matcher, and keeps a rolling reference catalog.
- UI & telemetry — rotation-correction indicator on the status bar, a
rotation constellation overlay and color legend on the star map, rotation
series on the guide graph, derotation settings on the Rotator pane, and
JSON-RPC support (
get_rotator_status,get_derotation,set_derotation,get_mount_geometry).
Setup, all of the settings, the field-rotation methods, monitoring, the server API,
and the configuration keys are documented in the in-app help topic "Alt-Az Guiding
and Field Derotation" (help/AltAz_Derotation.htm), reachable from the help
contents under that name. The Mount-geometry selector (Algorithms tab) and the
field-derotation controls (Rotator pane) are also cross-referenced from the Advanced
Settings help.
This fork tracks upstream PHD2 and is intended to remain mergeable with it. All added behavior is gated by mount geometry / derotation settings, so with an equatorial mount and derotation disabled PHD2-DrPi behaves like stock PHD2.
- Upstream project: https://github.com/OpenPHDGuiding
- Upstream web site: http://openphdguiding.org
See README.txt for the original PHD2 readme.