The avatar for @danleesmith
Dan Smith
Published
Edited
Oct 17, 2020
Fork of NOAA Solar Calculations
1 star
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latitude = -37.819982
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longitude = 144.983431
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datetime = moment.parseZone(`${d}T${t}${utc}`)
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EPOCH_DAY = datetime.hours(0).minutes(0).seconds(0)
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JD = (EPOCH_DAY / 86400000) + 2440587.5
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T = (JD - 2451545.0) / 36525
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L = 280.46646 + 36000.76983 * T + 0.0003032 * T**2
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M = 357.52911 + 35999.05029 * T + 0.0000001537 * T**2
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e = 0.016708634 - 0.000042037 * T - 0.0000001267 * T**2
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C = (1.914602 - 0.004817 * T - 0.000014 * T ** 2) * sin(M) + (0.019993 - 0.000101 * T) * sin(2 * M) + 0.000289 * sin(3 * M)
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sol = L + C
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v = M + C
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R = (1.000001018 * (1 - e ** 2)) / (1 + e * cos(v))
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λ = sol - 0.00569 - 0.00478 * sin(125.04 - 1934.136 * T)
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ε = 23 + 26 / 60 + 21.448 / 3600 - 46.8150 * T / 3600 - 0.00059 * T**2 / 3600 + 0.00183 * T**3 / 3600 + 0.00256 * cos(125.04 - 1934.136 * T)
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α = deg(Math.atan2(cos(ε) * sin(λ), cos(λ)))
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δ = deg(Math.asin(sin(ε) * sin(λ)))
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Ω = 125.04452 - 1934.136261 * T + 0.0020708 * T**2 + T**3 / 450000
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Δψ = -17.1196 * sin(Ω) - -1.3187 * sin(2 * (280.4665 + 36000.7698 * T)) - 0.2274 * sin(2 * (218.3165 + 481267.8813 * T)) + 0.2062 * sin(2 * Ω)
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θ = 100.46061837 + 36000.770053608 * T + 0.000387933 * T**2 - T**3 / 38710000 - Δψ * cos(ε) / 15
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H = (θ - longitude - α) % 360
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az = 180 - deg(Math.atan2(sin(H), cos(H) * sin(latitude) - tan(δ) * cos(latitude)))
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alt = deg(Math.asin(sin(latitude) * sin(δ) + cos(latitude) * cos(δ) * cos(H)))
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sin = (x) => Math.sin(rad(x))
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cos = (x) => Math.cos(rad(x))
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tan = (x) => Math.tan(rad(x))
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deg = (r) => r * 180 / Math.PI
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rad = (d) => d * Math.PI / 180
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