Crate astronomical_calculator 

Astronomical Calculator

A high-precision library for calculating solar position, sunrise/sunset times, and related astronomical phenomena.

This library provides accurate calculations of the Sun’s position and timing of solar events for any location on Earth. It accounts for atmospheric refraction, parallax, nutation, aberration, and other astronomical phenomena that affect solar position calculations.

This is a Rust port of the freespa library, based on VSOP87 theory. The library is no_std compatible, making it suitable for embedded systems and constrained environments.

Key Types

• AstronomicalCalculator - Main calculator struct for solar position and event calculations
• SolarPosition - Represents the Sun’s position with zenith and azimuth angles
• SolarEventResult - Result type for sunrise/sunset and twilight calculations
• Refraction - Atmospheric refraction model selection
• get_delta_t - Function to calculate ΔT (Terrestrial Time - Universal Time)

Basic Usage

use astronomical_calculator::{AstronomicalCalculator, Refraction};
use chrono::NaiveDateTime;

// Create a datetime (UTC)
let dt = NaiveDateTime::parse_from_str("2024-01-15 12:00:00", "%Y-%m-%d %H:%M:%S").unwrap().and_utc();

// Create calculator for New York City
// Note: longitude and latitude are in degrees
let mut calc = AstronomicalCalculator::new(
    dt,
    Some(69.0),        // delta_t: TT-UT in seconds (≈69s for 2024)
    0.0,               // delta_ut1: UT1-UTC in seconds
    -74.0,             // longitude in degrees (negative = West)
    40.7,              // latitude in degrees (positive = North)
    0.0,               // elevation in meters
    15.0,              // temperature in Celsius
    1013.0,            // pressure in millibars
    None,              // optional geometric dip angle
    Refraction::ApSolposBennetNA,  // refraction model (recommended for precision)
).unwrap();

// Get current solar position
let position = calc.get_solar_position();
println!("Zenith: {:.2}°", position.zenith.to_degrees());
println!("Azimuth: {:.2}°", position.azimuth.to_degrees());

// Get sunrise and sunset times (as Unix timestamps)
use astronomical_calculator::SolarEventResult;
match calc.get_sunrise().unwrap() {
    SolarEventResult::Occurs(timestamp) => {
        println!("Sunrise at Unix timestamp: {}", timestamp);
    }
    SolarEventResult::AllDay => println!("Sun never sets (midnight sun)"),
    SolarEventResult::AllNight => println!("Sun never rises (polar night)"),
}

Structs

AstronomicalCalculator

Main calculator for solar position and astronomical events.

JulianDate

Julian date and related time values for astronomical calculations.

SolarPosition

Solar position in local horizontal coordinates.

Enums

CalculationError

Errors that can occur during solar position calculations.

Refraction

Atmospheric refraction model selection.

SolarEventResult

Result of a solar event calculation (sunrise, sunset, twilight, etc.)

Functions

get_delta_t

Calculate ΔT (Terrestrial Time minus Universal Time) for a given date.