public static double calAlpha(double theta, double dec) {
if (Math.abs(dec) + theta > 89.9) return 180;
return (double)
Math.toDegrees(
Math.abs(
Math.atan(
Math.sin(Math.toRadians(theta))
/ Math.sqrt(
Math.cos(Math.toRadians(dec - theta))
* Math.cos(Math.toRadians(dec + theta))))));
}
