/** * @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); }