RA/Dec to Alt/Az PHP Class

This repository is a fork of Tom Gillespy's RA/Dec to Alt/Az repository, with the sole purpose of making the class composer installable. Some code refactoring was done, most importantly the class has been put into its own namespace.

This class converts celestial coordinates, along with the time, latitude and longditude to a altitude and azimuth for a telescope mount or camera.

##Installation

composer install leonboot/ra-dec-to-alt-az

##Usage

require 'vendor/autoload.php';

use Radec\Calculator as radec;

$radec = new radec(radec::decimaldegrees(latitude), radec::decimaldegrees(longditude));

$radec->setradec(radec::decimaldegrees(right_ascention), radec::decimaldegrees(declination));

$time = strtotime('now');

$azimuth = $radec->getAZ($time);
$altitude = $radec->getALT($time);

##Other Functions

####Radec\Calculator::daysbeforeJ2000($timestamp)

This gives the number of days between $timestamp and the J2000 epoch. Wikipedia Article

####Radec\Calculator::getdecimalUT($timestamp)

This gives the universitl time in decimal form. All calculations in this are performed using decimals from degrees, minutes and seconds and the time equivalent (hours, minuites and seconds).

####Radec\Calculator::fractionalday($timestamp)

This just divides the UT by 24 to get the fraction of a day.

####Radec\Calculator::getLST($timestamp)

This calculated Local Sidereal time for the latitude and longditude set in the constructor. The approximation is within 0.3 seconds of time for dates within 100 years of J2000.

####Radec\Calculator::getHA($timestamp)

Gets the current hour angle - the current angle of the observers location relative to the celestial sphere.

####Radec\Calculator::getALT($timestamp)

Returns the altitude of the specificed target at this time at a location.

####Radec\Calculator::getAZ($timestamp)

Returns the azimuth of the specified target at this time at a location.