The Moon's apparent position #5

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opened 2026-10-22 22:33:47 -05:00 by jeff · 0 comments

jeff commented

2026-10-22 22:33:47 -05:00

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Part of #1

Parent

What to build

astro.moon.position: the Moon's apparent position at an instant — ecliptic longitude and latitude, distance_km, right ascension and declination — from ch. 47's truncated ELP-2000/82 series (about 10″ in longitude). The documentation says how the accuracy degrades over the centuries.

Acceptance criteria

Ch. 47's worked example (1992 April 12) passes to the printed precision
The Moon's position is added to the Horizons reference tables for 1900–2100 and agrees within the stated tolerance
Properties: every finite result is in its documented range; NaN or ±∞ in gives NaN out
Every new public declaration has a doc comment giving units, time scale and reference frame, and citing the chapter and equation of Meeus it implements
Every source used is in the README's references cited
zig build test, zig build check, zig fmt --exclude zig-pkg --check . and reuse lint pass

Part of #1 ## Parent #1 ## What to build `astro.moon.position`: the Moon's **apparent position** at an **instant** — ecliptic longitude and latitude, `distance_km`, right ascension and declination — from ch. 47's truncated ELP-2000/82 series (about 10″ in longitude). The documentation says how the accuracy degrades over the centuries. ## Acceptance criteria - [ ] Ch. 47's worked example (1992 April 12) passes to the printed precision - [ ] The Moon's position is added to the Horizons reference tables for 1900–2100 and agrees within the stated tolerance - [ ] Properties: every finite result is in its documented range; NaN or ±∞ in gives NaN out - [ ] Every new public declaration has a doc comment giving units, time scale and reference frame, and citing the chapter and equation of Meeus it implements - [ ] Every source used is in the README's references cited - [ ] `zig build test`, `zig build check`, `zig fmt --exclude zig-pkg --check .` and `reuse lint` pass

jeff added the

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2026-10-22 22:33:48 -05:00

jeff added a new dependency

2026-10-22 22:33:51 -05:00

#3 Angles, coordinates, nutation and obliquity

jeff added a new dependency

2026-10-22 22:33:51 -05:00

#4 The Sun's apparent position

jeff added a new dependency

2026-10-22 22:33:52 -05:00