SpaceTime

Overview

• Conversion among equatorial coordinate (right ascension and declination), horizontal coordinate (azimuth and altitude), ecliptic coordinate (longitude and latitude) and their corresponding Cartesian equivalents.
• Calculate Julian Day and Local sidereal time.
• High precision calculation of the obliquity of ecliptic good to 0″.04 / 1000 years over 10000 years.
• Matrix / Quaternion transformation from celestial coordinate system to local tangent plane. Supports North-East-Down coordinate from earth-centered, earth-fixed coordinate system for any given longitude, latitude and timestamp.

Demo

You can find a demo project under SpaceTimeDemo directory. It showcases several useful scenarios.

Installation

Carthage

github "DJBen/SpaceTime" ~> 0.4.0

Usage

Equatorial to horizontal coordinate:

// Supply observer location and timestamp
let locTime = ObserverLocationTime(location: location, timestamp: JulianDay.now)
let vegaCoord = EquatorialCoordinate(rightAscension: radians(hours: 18, minutes: 36, seconds: 56.33635), declination: radians(degrees: 38, minutes: 47, seconds: 1.2802), distance: 1)
// Azimuth and altitude of Vega
let vegaAziAlt = HorizontalCoordinate.init(equatorialCoordinate: vegaCoord, observerInfo: locTime)

Ecliptic coordinate of Pollux at standard equinox of J2000.0.

let ra = DegreeAngle(116.328942)
let dec = DegreeAngle(28.026183)
let eclipticCoord = EclipticCoordinate(longitude: ra, latitude: dec, distance: 1, julianDay: .J2000)
eclipticCoord.longitude.wrappedValue // 113.21563
eclipticCoord.latitude.wrappedValue // 6.68417

Greenwich Mean Sidereal Time:

SiderealTime.init(julianDay: JulianDay.now)

Local Apparent Sidereal Time:

// Get location from GPS or hard code
let locTime = ObserverLocationTime(location: location, timestamp: JulianDay.now)
let localSidTime = SiderealTime.init(observerLocationTime: locTime)

More use cases can be found in the source and test cases.