diff --git a/README.en.md b/README.en.md index 11fd503..5460404 100644 --- a/README.en.md +++ b/README.en.md @@ -10,7 +10,7 @@ A personal astronomy library developed over years for calendrical-astronomy hobb The implementation follows *Astronomical Algorithms*; the covered scope is listed in [Highlights](#highlights) below. -The Sun and planets use built-in VSOP87-style analytical terms, while the Moon uses a built-in ELP/MPP02 DE405-fitted analytical series. No external JPL ephemeris files are required. +The Sun and planets use built-in VSOP87-style analytical terms, while the Moon uses a built-in truncated ELP2000/82-style analytical series. No external JPL ephemeris files are required. Unless noted otherwise, coordinates are apparent-of-date coordinates. Angles are in degrees, apparent diameters and semidiameters are in arcseconds, and distances use the unit implied by the function name, usually `AU` or `km`. @@ -104,7 +104,7 @@ This is suitable for ordinary calendrical work, observing support, outreach, and ### Moon -The Moon uses a built-in truncated ELP/MPP02 DE405-fitted analytical series retaining the major periodic terms. The package stays lightweight and does not require external ephemeris files. +The Moon uses a built-in truncated ELP2000/82-style analytical series. The package stays lightweight and does not require external ephemeris files. It is suitable for Chinese-calendar new moons, lunar phases, rise/set, lunar eclipses, amateur occultation prediction, and ordinary positional work; extremely high-precision lunar laser ranging, long-term physical libration, and professional occultation work fall outside that range and are best served by JPL or a dedicated lunar ephemeris. @@ -119,7 +119,7 @@ The matching `Next*`, `Last*`, and `Closest*` helpers are available in both nami ### Lite lightweight chains -`lite/sun` and `lite/moon` are independent approximation chains. They do not depend on the VSOP87 or ELP/MPP02 DE405 engines used by `sun` / `moon`, and are intended for CPU- or memory-constrained environments. +`lite/sun` and `lite/moon` are independent approximation chains. They do not depend on the VSOP87 or ELP2000/82 series used by `sun` / `moon`, and are intended for CPU- or memory-constrained environments. - `lite/sun`: simplified true/apparent solar longitude formulas plus lightweight equatorial conversion - `lite/moon`: Schlyter-style lunar approximation with about 15 perturbation terms plus lightweight topocentric correction @@ -172,7 +172,7 @@ The following entry points have been checked against JPL Horizons, NASA GSFC, IM - Moon rise/set: `aero=true` uses dynamic standard refraction and the instantaneous lunar semidiameter for an upper-limb crossing. Across 14 sea-level events at 7 sites, the current mean/maximum differences against JPL Horizons DE441 are about `0.30s / 0.75s`. - Moon rise/set with other conventions: mean/maximum differences are about `38.77s / 76.22s` against MET Norway's fixed `-0.8333°` convention. Against IMCCE Miriade, whose horizon convention is not exposed, the mean is about `2m13.46s`; the grazing `61°N` sample reaches about `6m41.82s`. - Earth perihelion and aphelion: maximum time difference about `1m28.84s`, maximum distance difference about `0.000000039837 AU` -- main-chain lunar position: the current algorithm is a truncated ELP/MPP02 DE405-fitted analytical series; across four JPL/Horizons `JDTT` samples in year `-2000`, the maximum difference from JPL/Horizons is about `219.6"` in longitude, `25.8"` in latitude, and `34.3 km` in distance +- main-chain lunar position: the current algorithm is a truncated ELP2000/82-style analytical series; across four JPL/Horizons `JDTT` samples in year `-2000`, the maximum difference from JPL/Horizons is about `219.6"` in longitude, `25.8"` in latitude, and `34.3 km` in distance - Moon perigee and apogee: maximum time difference about `15m53.45s`, maximum distance difference about `39.758 km` - maximum lunar declination: maximum time difference about `2.43s`, maximum declination difference about `0.00006431°` diff --git a/README.md b/README.md index 9ebe0bc..6ac29b8 100644 --- a/README.md +++ b/README.md @@ -8,7 +8,7 @@ >📚 本项目主要用于天文算法学习与验证，计算结果满足业余爱好级别需求。 -基于《天文算法》（Astronomical Algorithms）一书实现，覆盖范围见下方[功能概览](#功能概览)。太阳和行星部分使用内置 VSOP87 解析项，月球部分使用内置 ELP/MPP02（DE405 拟合）解析级数，不依赖外部 JPL 星历文件。 +基于《天文算法》（Astronomical Algorithms）一书实现，覆盖范围见下方[功能概览](#功能概览)。太阳和行星部分使用内置 VSOP87 解析项，月球部分使用内置 ELP2000/82 风格截断解析级数，不依赖外部 JPL 星历文件。 没有特殊标注时，本程序所提供的坐标均为瞬时天球坐标；角度单位默认是度，视直径/视半径单位是角秒，距离单位按函数名使用 AU 或 km。 @@ -103,11 +103,11 @@ go get b612.me/astro ### 月球 -月球使用内置的 ELP/MPP02 DE405 解析级数（截断版，保留主要周期项），库体积轻，不需要外部星历文件。它适合农历定朔、月相、升落、月食、业余月掩预报和常规位置计算；极高精度月球测距、长期物理天平动和专业掩星超出该范围，这类用途以 JPL 星历或专门月球星历为准。 +月球使用内置的 ELP2000/82 风格截断解析级数，库体积轻，不需要外部星历文件。它适合农历定朔、月相、升落、月食、业余月掩预报和常规位置计算；极高精度月球测距、长期物理天平动和专业掩星超出该范围，这类用途以 JPL 星历或专门月球星历为准。 ### Lite 轻量链路 -`lite/sun` 和 `lite/moon` 是独立于 `sun` / `moon` 的近似实现。不依赖 VSOP87 或 ELP/MPP02，适合 CPU / 内存受限环境。 +`lite/sun` 和 `lite/moon` 是独立于 `sun` / `moon` 的近似实现。不依赖 VSOP87 或主链的 ELP2000/82 级数，适合 CPU / 内存受限环境。 - `lite/sun`：简化太阳真黄经 / 视黄经公式 + 轻量赤道坐标转换 - `lite/moon`：Schlyter 风格月球近似（约 15 个摄动项）+ 轻量站心修正 @@ -162,7 +162,7 @@ go get b612.me/astro - 月出/月落：`aero=true` 按动态标准折射和实时月球视半径计算上缘过地平线。7 个地点、14 个海平面事件相对 JPL Horizons DE441 的平均/最大差异约 `0.30s / 0.75s` - 月出/月落的其他口径：相对固定 `-0.8333°` 的 MET Norway（Skyfield 1.53 + DE440s）约 `38.77s / 76.22s`；相对未公开地平线口径的 IMCCE Miriade 平均约 `2m13.46s`，`61°N` 低仰角样本最大约 `6m41.82s` - 地球近日点/远日点：时刻最大差异约 `1m28.84s`，距离最大差异约 `0.000000039837 AU` -- 月球主链位置：当前算法为 ELP/MPP02 DE405 解析级数截断版；在 `-2000` 年四个 JPL/Horizons `JDTT` 样本上，相对 JPL/Horizons 的最大差异约为黄经 `219.6"`、黄纬 `25.8"`、距离 `34.3 km` +- 月球主链位置：当前算法为 ELP2000/82 风格截断解析级数；在 `-2000` 年四个 JPL/Horizons `JDTT` 样本上，相对 JPL/Horizons 的最大差异约为黄经 `219.6"`、黄纬 `25.8"`、距离 `34.3 km` - 月球近地点/远地点：时刻最大差异约 `15m53.45s`，距离最大差异约 `39.758 km` - 月球最大赤纬：时刻最大差异约 `2.43s`，赤纬最大差异约 `0.00006431°`