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# Astro::Montenbruck

- [Astro::Montenbruck](#astromontenbruck)
  - [Overview](#overview)
  - [Precision](#precision)
  - [Contents](#contents)
  - [Requirements](#requirements)
  - [Installation](#installation)
  - [Documentation](#documentation)
  - [Scripts](#scripts)
    - [Example](#example)
  - [How to contribute](#how-to-contribute)
  - [License And Copyright](#license-and-copyright)
## Overview

Library of astronomical calculations, based on _"Astronomy On The Personal Computer"_ by _O.Montenbruck_ and _T.Phleger_, _Fourth Edition, Springer-Verlag, 2000_.

The main purpose of the library is to calculate positions of the Sun, the Moon, and the planets with precision that is approximately the same as that found in astronomical yearbooks. Other modules contain time-related routines, coordinates conversion...

Partially it overlaps some code which already exists in CPAN and elsewhere. For instance, there is a [Perl wrapper for Swiss Ephemeris](http://www.astrotexte.ch/sources/SwissEph.html). Swiss Ephemeris is fast and precise C library. Unfortunately, it ...

The present library is an attempt to find a middle-ground between precision on the one hand and compact, well organized code on the other. I tried to follow the best practices of modern Perl programming.

## Precision

As the book authors state in Introduction to the 4-th edition, _"The errors in the fundamental routines for determining the coordinates of the Sun, the Moon, and the planets amount to about 1″-3″._

## Contents

- [Astro::Montenbruck::MathUtils](lib/Astro/Montenbruck/MathUtils.pm) — Core mathematical routines.
- [Astro::Montenbruck::Time](lib/Astro/Montenbruck/Time.pm) — Time-related routines.
- [Astro::Montenbruck::Ephemeris](lib/Astro/Montenbruck/Ephemeris.pm) — Positions of celestial bodies.
- [Astro::Montenbruck::CoCo](lib/Astro/Montenbruck/CoCo.pm) — Coordinates conversions.
- [Astro::Montenbruck::NutEqu](lib/Astro/Montenbruck/NutEqu.pm) — Nutation and obliquity of ecliptic.
- [Astro::Montenbruck::RiseSet](lib/Astro/Montenbruck/RiseSet.pm) — Rise, set, transit and twilight time.
- [Astro::Montenbruck::Lunation](lib/Astro/Montenbruck/Lunation.pm) — Lunar phases
- [Astro::Montenbruck::SolEqu](lib/Astro/Montenbruck/SolEqu.pm) — Solstices and equinoxes


## Requirements

* __Perl__ >= 5.22

Tested on Linux 64-bit, macOS 10.14 and Windows 10 64-bit. There should be no problems at other platforms, as the code is pure Perl.

Perl dependencies are minimal, most of the external modules are part of the standard distribution.
[DateTime](https://metacpan.org/pod/DateTime) is not really required. It is used only in example scripts and tests, not the library itself.

## Installation

To install this module, run the following commands:

```
$ perl Build.PL
$ ./Build
$ ./Build installdeps
$ ./Build test
$ ./Build install
```

## Documentation

After installing, you can find documentation for this module with the perldoc command from the parent directory of the library:

```
$ perldoc Astro::Montenbruck
$ perldoc Astro::Montenbruck::Ephemeris
```

You may also generate local HTML documentation:

```
$ perl script/createdocs.pl
```

Documentation files will be installed to **docs/** directory.

## Scripts

[script/](script/) directory contains examples of the library usage. They will be extended over time.