Julia中如何计算日出日落时间？是否存在类似Python suntime、R suntimes的相关包？

Great question! While it might not have popped up right away on JuliaHub, there are actually a couple of solid Julia packages that can handle sunrise/sunset calculations—plus, if you’d rather avoid dependencies, you can implement the core astronomical algorithm manually. Here’s a breakdown of your options:

Existing Julia Packages #

1. AstroLib.jl #

This is a robust astronomy-focused package that includes a riseset function specifically designed to compute sunrise and sunset times. Here’s how you’d use it to replicate your Python example:

First, install the package if you haven’t already:

using Pkg
Pkg.add("AstroLib")

Then calculate sunset time for a given latitude, longitude, and date:

using AstroLib, Dates

# Define your coordinates and target date
LAT = 40.7128  # New York City latitude
LON = -74.0060 # New York City longitude
today = Dates.today()

# Compute sunrise and sunset (returns UTC times by default)
sunrise_utc, sunset_utc = riseset(LAT, LON, today)

# Convert to local time (example for UTC-5/Eastern Standard Time)
sunset_local = sunset_utc - Dates.Hour(5)

println("Local sunset time: ", sunset_local)

2. SunCalc.jl #

Ported from the popular JavaScript SunCalc library, this package offers a range of solar position calculations including sunrise/sunset. Install it with:

Pkg.add("SunCalc")

Usage example (returns local time by default):

using SunCalc, Dates

LAT = 40.7128
LON = -74.0060
today = Dates.now()

# Get sunset time as a DateTime object
sunset_time = SunCalc.get_sunset_time(LAT, LON, today)

println("Local sunset time: ", sunset_time)

Manual Implementation (If Packages Aren’t Ideal) #

If you prefer to avoid external dependencies, you can implement the NOAA sunrise/sunset algorithm directly. Here’s a simplified version that calculates sunset time in UTC:

using Dates

function calculate_sunset(lat::Float64, lon::Float64, date::Date)
    # Convert date to Julian day
    jd = Dates.datetime2julian(DateTime(date))
    
    # Julian century from J2000.0
    t = (jd - 2451545.0) / 36525.0
    
    # Sun's mean longitude
    L = mod(280.46646 + t*(36000.76983 + t*0.0003032), 360.0)
    
    # Sun's mean anomaly
    g = mod(357.52911 + t*(35999.05029 - t*0.0001537), 360.0)
    
    # Sun's ecliptic longitude
    lambda = L + 1.914602*t*sind(g) + 0.019993*t*t*sind(2*g) + 0.000289*t*t*t*sind(3*g)
    
    # Obliquity of the ecliptic
    epsilon = 23 + (26 + (21.448 - t*(46.8150 + t*(0.00059 - t*0.001813)))/60)/60
    epsilon_rad = deg2rad(epsilon)
    
    # Sun's right ascension and declination
    alpha = atan2(cosd(epsilon)*sind(lambda), cosd(lambda))
    delta = asind(sind(epsilon)*sind(lambda))
    
    # Local sidereal time
    lst = mod((jd - 2451545.0)*24 + 100.46 + 0.985647*jd + lon, 24)
    
    # Hour angle for sunset (using 90.833° for atmospheric refraction)
    h0 = acosd(cosd(90.833)/(cosd(lat)*cosd(delta)) - tand(lat)*tand(delta))
    
    # Sunset time in UTC hours
    sunset_hours = (lst - rad2deg(alpha) - h0)/15.0
    sunset_hours = mod(sunset_hours, 24.0)
    
    # Convert to DateTime object
    hours = floor(Int, sunset_hours)
    minutes = floor(Int, (sunset_hours - hours)*60)
    seconds = round(Int, ((sunset_hours - hours)*60 - minutes)*60)
    sunset_utc = DateTime(date) + Dates.Hour(hours) + Dates.Minute(minutes) + Dates.Second(seconds)
    
    return sunset_utc
end

# Example usage
LAT = 40.7128
LON = -74.0060
today = Dates.today()
sunset_utc = calculate_sunset(LAT, LON, today)

println("UTC sunset time: ", sunset_utc)

This manual implementation follows the NOAA algorithm and gives you full control over the calculation without relying on external packages.

内容的提问来源于stack exchange，提问作者Thomas