/**
* @covers Marando\Meeus\Nutation\Nutation::find
* @see p.148, ex. 22.a
*/
public function testFind()
{
$n = Nutation::find(AstroDate::parse('1987-Apr-10'));
$this->assertEquals(-3.788 / 3600, $n->long->deg, 'Δψ', 1.0E-6);
$this->assertEquals(+9.443 / 3600, $n->obli->deg, 'Δε', 1.0E-6);
}
/**
* 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);
}
