sun position icon

[fche]

It would be cute to have an option for a yellow dot that shows the current overhead position of the sun.

[joergdietrich]

Thanks for your suggestion. I would welcome a PR to make this is a configurable option. It's not a high priority for me to work on.

[makrolika]

Okay ... here is also already an issur for that.
duplicate: #29

here a trial:

we need a Nutation, and the variables dphi and eps.

//	Nutation (good to 0.5 arcsec in dphi and 0.1 arcsec in depsilon)
//	returns dphi and depsilon in an array in radians so the
//	array can be added to ecliptic coords

function nutation(day) {
	var t = day /36525;
	var Om = angle(125.04452 - 1934.136261 * t);
	var Lm = angle(218.3165 + 481267.8813 * t);
	var Ls = angle(280.4665 + 36000.7698 * t);	
	var dphi = -17.20 * Math.sin(Om) - 1.32 * Math.sin(2 * Ls) 
				- 0.23 * Math.sin(2 * Lm) + 0.21 * Math.sin(2 * Om);
	var deps = 9.20 * Math.cos(Om) + 0.57 * Math.cos(2 * Ls) 
				+ 0.10 * Math.cos(2 * Lm) - 0.09 * Math.cos(2*Om);
	// nut = new Array(0, 0, 0, 0);
	// nut[1] = dphi * DEG2RAD /3600;
	// nut[2] = deps * DEG2RAD / 3600;

// edit
var eps = deps + ((84381.448 - 46.815 * TE - 0.00059 * TE2 + 0.001813 * TE3) / 3600);

	return {'dphi':dphi, 'eps':eps};
}

var DEG2RAD = Math.PI / 180;
var RAD2DEG = 180 / Math.PI;
var TwoPi = Math.PI * 2;

function angle(deg) {
    return range(deg) * DEG2RAD;
}
function ipart(x) {
	var a;
	if (x > 0) {
	    a = Math.floor(x);
	} else {
	    a = Math.ceil(x);
	}	
	return a;
}
function range(x) {
	var a, b
	b = x / 360;
	a = 360 * (b - ipart(b));
	if (a < 0 ) {
	    a = a + 360
	}
	return a
}

source code: https://www2.arnes.si/~gljsentvid10/jmoonpos.html

we need a Aries, and the variable GHAAtrue.

function Aries() {
	GHAAtrue = norm(norm(280.46061837 + 360.98564736629 * (JD - 2451545) + 0.000387933 * T2 - T3 / 38710000) + dphi * cosd(eps));
}

function sind(degree) {
	return Math.sin(DEG2RAD * degree);
}
function cosd(degree) {
	return Math.cos(DEG2RAD * degree);
}
function tand(degree) {
	return Math.tan(DEG2RAD * degree);
}
function norm(degree) {
	return (360 * (degree / 360 - Math.floor(degree / 360)));
}

source code: https://repositorio.unican.es/xmlui/bitstream/handle/10902/13373/Pascual%20Caba%C3%B1ero,%20Mar%C3%ADa.pdf

we need a variable GHAsun (Longitude position of the sun in a map) and use the _sunEquatorialPosition.alpha:

GHAsun = norm(GHAAtrue - _sunEquatorialPosition.alpha);

untestet.