26 lines
903 B
Go
26 lines
903 B
Go
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package basic
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import (
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"math"
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. "b612.me/astro/tools"
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)
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// ParallacticAngleByHourAngle 返回视差角（天顶方向角）/ parallactic angle.
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//
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// hourAngle 为目标时角，dec 为赤纬，lat 为观测者纬度，单位均为度。
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// 返回值是 atan2 公式给出的有符号结果，范围通常为 [-180, 180] 度。
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// hourAngle may be signed or normalized to [0, 360); the trigonometric
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// formula handles either representation.
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func ParallacticAngleByHourAngle(hourAngle, dec, lat float64) float64 {
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return math.Atan2(
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Sin(hourAngle),
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Tan(lat)*Cos(dec)-Sin(dec)*Cos(hourAngle),
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) * 180 / math.Pi
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}
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// StarParallacticAngle 返回星体在给定观测条件下的视差角（天顶方向角）/ parallactic angle.
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func StarParallacticAngle(jde, ra, dec, lon, lat, timezone float64) float64 {
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return ParallacticAngleByHourAngle(StarHourAngle(jde, ra, lon, timezone), dec, lat)
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}
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