/**
* Converts this instance to an equatorial coordinate
*
* @return Equat
*/
public function toEquat()
{
// Cartesian -> spherical
IAU::C2s([$this->x->au, $this->y->au, $this->z->au], $theta, $phi);
// Create RA and Declination components from radians
$ra = Angle::rad($theta)->norm()->toTime();
$dec = Angle::rad($phi);
// Return new equatorial instance using same frame and epoch
return new Equat($this->frame, $this->epoch, $ra, $dec, $this->r);
}
/**
* Calculates the offset of this time zone for a given Julian date. Accounts
* for daylight savings time if relevant and based on the date.
*
* @param float $jd Julian date to check for
* @return float Offset in hours including DST (if relevant)
*/
public function offset($jd)
{
// Is DST observed for this timezone? If no, return offset as is
if ($this->dst == false) {
return $this->offset;
}
// Get YMD for provided JD and day of year number (with fractional day)
IAU::Jd2cal($jd, 0, $y, $m, $d, $fd);
$dayN = static::dayOfYear($y, $m, $d) + $fd;
// DST begins at 2:00 a.m. on the second Sunday of March and...
IAU::Cal2jd($y, 3, 1, $djm0, $djm);
$dayB = static::dayOfYear($y, 2, 1) + 14 - static::weekDayNum($djm0 + $djm) + 2 / 24;
// ...ends at 2:00 a.m. on the first Sunday of November
IAU::Cal2jd($y, 11, 1, $djm0, $djm);
$dayE = static::dayOfYear($y, 11, 1) + 14 - static::weekDayNum($djm0 + $djm) + 2 / 24;
// Check if the given JD falls with in the DST range for that year
if ($dayN >= $dayB && $dayN < $dayE) {
return $this->offset + 1;
} else {
return $this->offset;
}
}
/**
* Performs a [IRCS -> observed] coordinate transformation for the parameters
* of this instance
* @param string $type Coordintate type, 'e' for equat 'h' for horiz
* @return static|Horiz
*/
protected function ICRStoObserved($type = 'e', Pressure $pressure = null, Temperature $temp = null, $humidity = null)
{
// Instance initial properties
$rc = $this->ra->toAngle()->rad;
$dc = $this->dec->rad;
$date1 = $this->epoch->toDate()->toTDB()->toJD();
$pr = 0;
$pd = 0;
$rv = 0;
$px = $this->dist->au > 0 ? 8.794 / 3600 / $this->dist->au : 0;
$utc1 = $this->epoch->toDate()->toUTC()->toJD();
$dut1 = IERS::jd($utc1)->dut1();
$elong = $this->topo ? $this->topo->lon->rad : 0;
$phi = $this->topo ? $this->topo->lat->rad : 0;
$hm = 0;
//$this->obsrv->height->m;
$xp = IERS::jd($utc1)->x() / 3600 * pi() / 180;
$yp = IERS::jd($utc1)->y() / 3600 * pi() / 180;
$phpa = $pressure ? $pressure->mbar : 0;
$tc = $temp ? $temp->c : 0;
$rh = $humidity ? $humidity : 0;
$wl = 0.55;
// ICRS -> CIRS (geocentric observer)
IAU::Atci13($rc, $dc, $pr, $pd, $px, $rv, $date1, 0, $ri, $di, $eo);
// CIRS -> ICRS (astrometric)
//IAU::Atic13($ri, $di, $date1, 0, $rca, $dca, $eo);
// ICRS (astrometric) -> CIRS (geocentric observer)
//IAU::Atci13($rca, $dca, $pr, $pd, $px, $rv, $date1, 0, $ri, $di, $eo);
// Apparent place ?
//$ri = $ri - $eo;
//$di = $di;
//
// CIRS -> topocentric
IAU::Atio13($ri, $di, $utc1, 0, $dut1, $elong, $phi, $hm, $xp, $yp, $phpa, $tc, $rh, $wl, $aob, $zob, $hob, $dob, $rob);
if ($type == 'e') {
// Copy this instance, and override the apparent RA and Decl
$topocentric = $this->copy();
$topocentric->ra = Angle::rad($rob)->toTime();
$topocentric->dec = Angle::rad($dob);
$topocentric->apparent = true;
// Return apparent coordinates
return $topocentric;
} else {
// Prepare new horizontal instance
$horiz = new Horiz(Angle::rad(deg2rad(90) - $zob), Angle::rad($aob), $this->dist);
return $horiz;
}
}
/**
* Gets a component of this date
*
* @param string $e Component name, e.g. year, month, etc...
* @return int|float
*/
protected function getComponent($e)
{
// JD -> Date
$ihmsf = [];
IAU::D2dtf($this->timescale, $this->prec - 2, $this->jd, $this->dayFrac, $iy, $im, $id, $ihmsf);
switch ($e) {
case 'year':
return $iy;
case 'month':
return $im;
case 'day':
return $id;
case 'hour':
return $ihmsf[0];
case 'min':
return $ihmsf[1];
case 'sec':
return $ihmsf[2];
case 'micro':
return $ihmsf[3];
}
}
