getMoonIllumination

moon-sighting v1.1.1

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moon-sighting / getMoonIllumination

Function: getMoonIllumination()

getMoonIllumination(date?): MoonIlluminationResult

Defined in: api/index.ts:592

Compute the Moon's illumination fraction, phase cycle position, and bright limb angle.

Works WITHOUT a kernel (uses Meeus Ch. 47/48 approximation). Accuracy: illumination fraction ~0.5%, phase fraction ~0.003. Drop-in replacement for suncalc.getMoonIllumination() — same field names and conventions.

Parameters

date?

Date = ...

Date to compute illumination for (default: now)

Returns

MoonIlluminationResult

fraction (0-1), phase (0-1 cycle), angle (bright limb position angle, radians), isWaxing

Example

const illum = getMoonIllumination(new Date())
console.log(illum.fraction)  // e.g. 0.43 (43% illuminated)
console.log(illum.phase)     // e.g. 0.18 (waxing crescent territory)