/**
* @covers Marando\Meeus\Nutation\Nutation::trueObliquity
* @see p.148, ex. 22.a
*/
public function testTrueObliquity()
{
$ε = Nutation::trueObliquity(AstroDate::parse('1987-Apr-10'));
$this->assertEquals(23, $ε->d, 'd');
$this->assertEquals(26, $ε->m, 'm');
$this->assertEquals(36.85, $ε->s, 's', 0.01);
}
/**
* Finds the true obliquity of the ecliptic (ε = ε0 + Δε) for a given date.
*
* @param AstroDate $date Date to calculate the ε for
* @return Angle True obliquity of the ecliptic (ε)
*/
public static function trueObliquity(AstroDate $date)
{
$n = Nutation::find($date);
$ε0 = static::meanObliquity($date);
// ε = ε0 + Δε
return $ε = $ε0->add($n->obli);
}
