l0 function
Mean longitude of the Sun, L0, from (28.2) p. 183.
tau is in Julian millennia from J2000.0.
Returns L0 in degrees.
Implementation
double l0(double tau) {
return horner(tau, [
280.4664567,
360007.6982779,
0.03032028,
1 / 49931,
-1 / 15300,
-1 / 2000000,
]);
}