Perform sight reductions and plot positions from celestial observations.
This maintained fork adds:
- a time-integrity panel showing local, UTC, GNSS/NMEA and chrony status;
- an optional persistent show/hide control for the time panel; and
- observed sunrise/sunset horizon events, with optional magnetic or true bearing, magnetic variation, compass deviation and uncertainty estimates;
- a fully offline Sun, Moon and sight planner with twilight/rise/set/transit tables, Moon phase information, navigational-body sky plot, best pair/triad ranking and CSV almanac export;
- a Generate Almanac… workflow which creates a route- or position-aware, completely offline voyage PDF with hourly Sun/Moon/Aries and navigational- planet ephemerides, all 57 navigational stars, sight recommendations, lunar opportunities, correction/reduction references and working forms. A saved route can be selected in the generator, or the same workflow can be opened pre-populated using Generate fallback almanac… on an OpenCPN route's context menu; The generator ranges from a compact Passage Brief to a full global annual edition. Its calculator-free safety level enforces hourly ephemerides, minute/second and v/d interpolation tables, altitude corrections, voyage-specific direct Hc/Zn lookup tables, universal Ageton reduction tables, instructions and forms. Optional planning graphs and booklet signature imposition are included;
- a time-tagged numerical running fix which advances each observation through a COG/SOG motion model to a common epoch;
- a sight-sequence analyzer for residuals, scatter, robust outliers, trend and personal bias, plus dedicated noon and Polaris helpers;
- a rebuilt lunar-distance workflow which supports simultaneous or separately time-tagged lunar distance/Moon altitude/body altitude readings, searches for every matching UTC in a selectable interval, jointly recovers a constant watch offset and reference-epoch position, optionally advances a moving vessel by COG/SOG, and reports numerical time/position uncertainty;
- coastal sextant tools for vertical-angle ranges, optional bearing/range positions, one-angle chart loci and numerical three-object/two-angle fixes;
- a working celestial-body azimuth sight, explicitly distinguished from a terrestrial horizontal sextant angle; and
- a completely offline solar-eclipse planner powered by JPL DE440, with event discovery through 2100, local C1–C4 circumstances, central-path limits, partial-eclipse magnitude contours and optional NASA LOLA lunar-limb contact refinement.
The eclipse planner is opened with Eclipses… on the plugin's main window.
Its astronomical data is deliberately separate from the plugin binary. The
complete runtime data set is kept in eclipse/data using Git LFS: the DE440s
base kernel and the optional lunar-orientation and converted LOLA packs. Use
the three Import buttons once to copy these checksum-verified files from
the checkout into OpenCPN's private plugin-data directory. No eclipse
calculation or UI action performs network access. See
eclipse/DATA.md for exact files, provenance, checksums and
storage sizes. Whole-file HTTPS downloads, including SHA256SUMS and the
three source manifests, are also available from the
offline eclipse data 2026.1 release;
Git LFS is not required when using those release assets.
The ordinary navigation planner is independent of the eclipse data packs. It uses the plugin's bundled VSOP87D, ELP2000 and navigational-star data, works without DE440 or LOLA, and never requires a network connection. Lunar distances use the locally installed DE440s kernel when it is present and fall back to the bundled analytical catalogue otherwise; LOLA is never required. See the offline planning and running-fix guide. The separate lunar-distance and coastal-sextant guide explains the simultaneous and sequential observation models, unknown-watch-offset workflow, genuine position ambiguity, controls and limitations.
The almanac can now be calculator-free: after printing, a navigator can reduce and plot supported sights using the document, sextant, accurate watch, pencil and plotting tools, without a computer, internet connection, scientific calculator or external almanac. The cover carries a machine-checked dependency manifest. See the implementation and performance note.
Maintained fork: https://github.com/pob220/celestial_navigation_pi
Upstream maintenance repository: https://github.com/rgleason/celestial_navigation_pi
Original source repository: https://github.com/seandepagnier/celestial_navigation_pi
Install Git LFS before cloning so the offline eclipse data is checked out as
real binary files rather than small LFS pointer files. Alternatively, download
the whole files and SHA256SUMS from the
offline eclipse data release.
git lfs installgit clone --recurse-submodules https://github.com/pob220/celestial_navigation_pi.gitcd celestial_navigation_pigit lfs pull
The three eclipse files should then be present at:
eclipse/data/de440s.bspeclipse/data/moon_pa_de440_200625.bpceclipse/data/lola64-pa.bin
Their sizes and SHA-256 digests are pinned in the adjacent manifests. The normal celestial-navigation, planning and almanac features do not require these files. DE440s is required only by the eclipse planner; the orientation and LOLA files add optional lunar-limb contact refinement.
Under windows, you must find the file "opencpn.lib" (Visual Studio) or "libopencpn.dll.a" (mingw) which is built in the build directory after compiling opencpn. This file must be copied to the plugin directory.
Build as normally:
cmake -S . -B build -DCMAKE_BUILD_TYPE=Releasecmake --build buildcmake --install build
After installing or loading the plugin, open Eclipses… and import the
three files from eclipse/data. This is a local copy operation and requires no
network access.
cmake -S . -B build -DOCPN_BUILD_TEST=ONcmake --build buildctest --test-dir build --output-on-failure
The standalone eclipse engine retains its own independent regression suite in
eclipse/tests.
The plugin code is licensed under the terms of the GPL v3 or, at your will, later.