/**
* Calculates the sidereal time for the given timestamp.
*
* @return float
*/
public function getSiderealTime()
{
$julianDay = new JulianDay($this->dateTime);
$T = bcdiv(bcsub(strval($julianDay), '2451545.0'), '36525');
$T2 = bcpow($T, '2');
$T3 = bcpow($T, '3');
$term1 = '280.46061837';
$term2 = bcmul('360.98564736629', bcsub(strval($julianDay), '2451545.0'));
$term3 = bcmul('0.000387933', $T2);
$term4 = bcdiv($T3, '38710000');
$result = bcsub(bcadd(bcadd($term1, $term2), $term3), $term4);
while (bccomp($result, 0) == -1) {
$result = bcadd($result, '360');
}
while (bccomp($result, '360') >= 1) {
$result = bcsub($result, '360');
}
$st = new Time();
$st->setHourAngle(floatval($result));
return $st->getValue();
}
public function testSetHourAngleWorksAsExpected()
{
$time = new Time();
$time->setHourAngle(100.596390417);
$this->assertEquals(6.7064260278, $time->getValue());
}
/**
* Create the DateTime object for the given Julian Day
*
* @link http://www.tondering.dk/claus/cal/julperiod.php
*
* @param float $julianDay
*
* @return \DateTime
*/
protected function julianDayToDatetime($julianDay)
{
$J = $julianDay + 0.5;
$Z = intval($J);
$F = $J - $Z;
$A = $Z;
if ($Z >= 2299161) {
$a = $this->intDiv($Z - 1867216.25, 36524.25);
$A = $Z + 1 + $a - $this->intDiv($a, 4);
}
$B = $A + 1524;
$C = $this->intDiv($B - 122.1, 365.25);
$D = intval(365.25 * $C);
$E = $this->intDiv($B - $D, 30.6001);
$day = $B - $D - intval(30.6001 * $E) + $F;
if ($E < 14) {
$month = $E - 1;
} else {
$month = $E - 13;
}
if ($month > 2) {
$year = $C - 4716;
} else {
$year = $C - 4715;
}
$decimalDayTime = $day - intval($day);
$time = new Time(24 * $decimalDayTime);
$hour = $time->getHour();
$minute = $time->getMinute();
$second = $time->getSecond();
$dateTime = new \DateTime(sprintf('%04d-%02d-%02d %02d:%02d:%02d', $year, $month, $day, $hour, $minute, $second), new \DateTimeZone('UTC'));
return $dateTime;
}