Algorithms from "[Practical Astronomy with your Calculator or Spreadsheet](https://www.amazon.com/Practical-Astronomy-your-Calculator-Spreadsheet/dp/1108436072)" by Peter Duffett-Smith, implemented in .NET 6.

If you're interested in this topic, please buy the book! It provides far more detail and context.

Getting Started (for clients)

Create a console application:

dotnet new console -o PAConsoleTest
 
cd PAConsoleTest

Using the NuGet package is the easiest way to consume the library in a client application. Add a NuGet reference for the Practical Astronomy library, following the directions here.

Open Program.cs, and make a few changes. First, add a using statement for Practical Astronomy:

using PALib;

PALib

Definition BinaryData.cs:4

Then, replace the 'Hello World' boilerplate with this:

// Coordinates test (angle degrees to decimal degrees)
var paCoordinates = new PALib.PACoordinates();
 
var decimalDegrees = Math.Round(paCoordinates.AngleToDecimalDegrees(182, 31, 27), 3);
 
Console.WriteLine($"Decimal degrees value is {decimalDegrees}");
 
// Moon test (approximate moon phase)
var paMoon = new PALib.PAMoon();
 
var (moonPhase, brightLimbDegrees) = paMoon.MoonPhase(0, 0, 0, false, 0, 1, 9, 2003, PAAccuracyLevel.Approximate);
 
Console.WriteLine($"Moon phase value is {moonPhase}, bright limb degrees value is {brightLimbDegrees}");

When you run, you should see this:

Decimal degrees value is 182.524

Moon phase value is 0.22, bright limb degrees value is -71.58

Library Functions - Status

Date/Time

[x] Calculate -> Date of Easter
[x] Convert -> Civil Date to Day Number
[x] Convert -> Civil Time <-> Decimal Hours
[x] Extract -> Hour, Minutes, and Seconds parts of Decimal Hours
[x] Convert -> Local Civil Time <-> Universal Time
[x] Convert -> Universal Time <-> Greenwich Sidereal Time
[x] Convert -> Greenwich Sidereal Time <-> Local Sidereal Time

Coordinates

[x] Convert -> Angle <-> Decimal Degrees
[x] Convert -> Right Ascension <-> Hour Angle
[x] Convert -> Equatorial Coordinates <-> Horizon Coordinates
[x] Calculate -> Obliquity of the Ecliptic
[x] Convert -> Ecliptic Coordinates <-> Equatorial Coordinates
[x] Convert -> Equatorial Coordinates <-> Galactic Coordinates
[x] Calculate -> Angle between two objects
[x] Calculate -> Rising and Setting times for an object
[x] Calculate -> Precession (corrected coordinates between two epochs)
[x] Calculate -> Nutation (in ecliptic longitude and obliquity) for a Greenwich date
[x] Calculate -> Effects of aberration for ecliptic coordinates
[x] Calculate -> RA and Declination values, corrected for atmospheric refraction
[x] Calculate -> RA and Declination values, corrected for geocentric parallax
[x] Calculate -> Heliographic coordinates
[x] Calculate -> Carrington rotation number
[x] Calculate -> Selenographic (lunar) coordinates (sub-Earth and sub-Solar)

The Sun

[x] Calculate -> Approximate and precise positions of the Sun
[x] Calculate -> Sun's distance and angular size
[x] Calculate -> Local sunrise and sunset
[x] Calculate -> Morning and evening twilight
[x] Calculate -> Equation of time
[x] Calculate -> Solar elongation

Planets

[x] Calculate -> Approximate position of planet
[x] Calculate -> Precise position of planet
[x] Calculate -> Visual aspects of planet (distance, angular diameter, phase, light time, position angle of bright limb, and apparent magnitude)
[x] Calculate -> Position of comet (elliptical and parabolic)
[x] Calculate -> Binary star orbit data

The Moon

[x] Calculate -> Approximate and precise position of Moon
[x] Calculate -> Moon phase and position angle of bright limb
[x] Calculate -> Times of new Moon and full Moon
[x] Calculate -> Moon's distance, angular diameter, and horizontal parallax
[x] Calculate -> Local moonrise and moonset

Eclipses

[x] Calculate -> Lunar eclipse occurrence and circumstances
[x] Calculate -> Solar eclipse occurrence and circumstances