private void btnCalculate_Click(object sender, EventArgs e)
{
double sunRA;
double sunDec;
double sunDistance;
AstroUtilities.QuickPlanet(TimeOfMinimumJD, 3, true, out sunRA, out sunDec, out sunDistance);
double dDeg = AstroConvert.ToDeclination(tbxDE.Text);
double raHours = AstroConvert.ToRightAcsension(tbxRA.Text);
double dRad = dDeg * Math.PI / 180.0;
double raRad = raHours * 15 * Math.PI / 180.0;
double C = 299792458.0; // m/s
// HJD = JD - (r/c) * [sin(d) * sin (dSun) + cos(d) * cos (dSun) * cos (a - aSun)]
double correction = (sunDistance * 1.4960E11 / C) * (Math.Sin(dRad) * Math.Sin(sunDec) + Math.Cos(dRad) * Math.Cos(sunDec) * Math.Cos(raRad - sunRA));
double hjd = TimeOfMinimumJD - (correction / (3600 * 24));
tbxCorrection.Text = hjd.ToString();
TimeOfMinimumHJD = hjd;
TimeCorrectionHJD = -(correction / (3600 * 24));
}
