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https://github.com/mjaschen/astrotools
General Purpose Astronomy Library for PHP
https://github.com/mjaschen/astrotools
Last synced: 3 months ago
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General Purpose Astronomy Library for PHP
- Host: GitHub
- URL: https://github.com/mjaschen/astrotools
- Owner: mjaschen
- Created: 2015-03-04T14:13:20.000Z (almost 10 years ago)
- Default Branch: main
- Last Pushed: 2021-03-30T06:09:02.000Z (almost 4 years ago)
- Last Synced: 2024-10-10T12:40:05.321Z (3 months ago)
- Language: PHP
- Size: 54.7 KB
- Stars: 4
- Watchers: 3
- Forks: 3
- Open Issues: 1
-
Metadata Files:
- Readme: README.md
- Changelog: CHANGELOG.md
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README
# Astrotools
Astrotools is a general purpose PHP library for astronomy.
## Requirements
* PHP >= 7.3
* *bcmath* extension
### Older PHP versions
- 0.1.x branch supports PHP >= 7.0
- 0.0.x branch supports PHP 5.4 - 5.6. For details see the next section.
## Installation
```shell
composer require mjaschen/astrotools
```
### PHP 7.0, PHP 7.1, PHP 7.2
If you need to use Astrotools with PHP 7.0, 7.1 or 7.2 just require version 0.1:
```shell
composer require mjaschen/astrotools:^0.1.0
```
Please keep in mind, that the 0.1.x branch is no longer maintained and won't get any updates.
### PHP 5
If you need to use Astrotools with PHP 5.4, 5.5, or 5.6, just require version 0.0.2:
```shell
composer require mjaschen/astrotools:0.0.2
```
Please keep in mind, that the 0.0.x branch is no longer maintained and won't get any updates.
## Features
* Julian day calculation (forward/reverse)
* Sidereal time calculation (GMST, local sidereal time)
* Date of Easter calculation
* Time helper
## Why not use PHP's calendar extension?
Some implemented features (e.g. calculation of Julian day or Date of Easter) are already provided by PHP's [calendar](http://php.net/manual/en/ref.calendar.php) extension.
These functions come with some problems, e.g. `easter_date()` can only calculate the Date of Easter for the timerange of unix timestamps (1970 January 1 to somewhere around 2037/2038).
## Usage Examples
### Calculation of the Julian day from Date/Time
```php
use Astrotools\Time\JulianDay;
$timestamp = new \DateTime('2015-02-25 12:01:36', new \DateTimeZone('Europe/Berlin'));
$jd = JulianDay::fromDateTime($timestamp);
echo $jd->getValue();
```
The code above produces the output shown below:
```
2459283.3831366
```
### Calculation of Date/Time from Julian day
```php
use Astrotools\Time\JulianDay;
$jd = new JulianDay(2451545.0);
var_dump($jd->getDateTime());
```
The code above produces the output shown below:
```
class DateTime#10 (3) {
public $date =>
string(26) "2000-01-01 12:00:00.000000"
public $timezone_type =>
int(3)
public $timezone =>
string(3) "UTC"
}
```
### Calculation of sidereal time for a given Date/Time
#### Greenwich sidereal time
```php
use Astrotools\Time\SiderealTime;
$dt = new \DateTime('2007-12-25 00:00:00', new \DateTimeZone('UTC'));
$st = new SiderealTime($dt);
echo $st->getSiderealTime();
```
The code above produces the output shown below:
```
6.2086583333
```
#### Local sidereal time
Local sidereal time for Berlin, Germany (longitude = 13.5 degrees east):
```php
use Astrotools\Time\SiderealTime;
$dt = new \DateTime('2007-12-25 20:00:00', new \DateTimeZone('UTC'));
$st = new SiderealTime($dt);
echo $st->getLocalSiderealTime(13.5);
```
The code above produces the output shown below:
```
3.1634161794
```
### Time helper
#### Convert hours, minutes, and seconds to decimal time
```php
use Astrotools\Helper\Time;
$time = Time::fromTime(6, 42, 23.1337);
echo $time->getValue();
```
The code above produces the output shown below:
```
6.7064260278
```
#### Convert decimal time to hours, minutes, and seconds
```php
use Astrotools\Helper\Time;
$time = new Time(6.7064260278);
printf('%02d:%02d:%02.4f', $time->getHour(), $time->getMinute(), $time->getSecond());
```
The code above produces the output shown below:
```
06:42:23.1337
```
#### Convert between time and hour angle
```php
use Astrotools\Helper\Time;
$time = Time::fromTime(6, 42, 23.1337);
echo $time->getHourAngle() . PHP_EOL;
echo Time::fromHourAngle(275)->getValue();
```
The code above produces the output shown below:
```
100.596390417
18.333333333333
```
### Date of Easter Calculation
```php
use Astrotools\Time\DateOfEaster;
$doe = new DateOfEaster(2000);
echo $doe->getDate()->format('Y-m-d');
```
The code above produces the output shown below:
```
2000-04-23
```
### Calculation of ΔT
There exist multiple methods to get the value of ΔT for a given (decimal) year.
One can lookup the value in [tables](http://maia.usno.navy.mil/) and interpolate
it for the wanted date or calculate it using
[polynomial expressions](http://eclipse.gsfc.nasa.gov/SEcat5/deltatpoly.html).
*Astrotools* currently provides the calculation of ΔT with polynomial
expressions. Reasonably accurate values are provided for the timespan between
the years -500 and 2150.
```php
getDeltaT(2016.125);
```
The code above produces the output shown below:
```
69.568218578125
```
## Todo
* Support for microseconds in Julian day calculation
* Implement ΔT determination by table lookups
## References
* [Julian day formula - Astronomical Applications Department of the U.S. Naval Observatory](http://aa.usno.navy.mil/faq/docs/JD_Formula.php)
* [Julian Date Converter - Astronomical Applications Department of the U.S. Naval Observatory](http://aa.usno.navy.mil/data/docs/JulianDate.php)
* [Julian day - Wikipedia](http://en.wikipedia.org/wiki/Julian_day)
* [ΔT](https://en.wikipedia.org/wiki/%CE%94T)
* Astronomical Algorithms, Jean Meuss, 1998, ISBN 978-0943396613
* [Polynomial Expressions For Delta T (ΔT)](http://eclipse.gsfc.nasa.gov/SEcat5/deltatpoly.html)