/**
* Rise and Set of Sun and Moon of Earth planet in current galaxy
* (address: Local Bubble in Local Interstellar Cloud of Orion–Cygnus Arm, for more coordinats ask Frank the Pug or agent K)
*/
no_rs = {
hours: '--',
minutes: '--'
};
function GetRiseSet(glat,glong) {
var OutString = "";
var calend;
var quady = new Array;
var sunp = new Array;
var moonp = new Array;
var y, m, day, tz, mj, lst1, i;
var rads = 0.0174532925, sinmoonalt;
//
// parse the form to make sure the numbers are numbers and not strings!
//
var d = new Date();
y = d.getFullYear();
m = d.getMonth()+1;
day = d.getDate();
tz = -d.getTimezoneOffset()/60;
//
// main loop. All the work is done in the functions with the long names
// find_sun_and_twi_events_for_date() and find_moonrise_set()
//
mj = mjd(day, m, y, 0.0);
return {
sun: find_sun_and_twi_events_for_date(mj, tz, glong, glat),
moon: find_moonrise_set(mj, tz, glong, glat)
};
} // end of main program
function hrsmin(hours) {
//
// takes decimal hours and returns a string in hhmm format
//
var hrs, h, m, dum;
hrs = Math.floor(hours * 60 + 0.5)/ 60.0;
h = Math.floor(hrs);
m = Math.floor(60 * (hrs - h) + 0.5);
dum = String(h) + ':' + String(m);
//
// the jiggery pokery below is to make sure that two minutes past midnight
// comes out as 0002 not 2. Javascript does not appear to have 'format codes'
// like C
//
if(m < 10)
m = '0'+String(m);
if(h < 10)
h = '0'+String(h);
return {
hours: h,
minutes: m
};
}
function ipart(x) {
//
// returns the integer part - like int() in basic
//
var a;
if (x> 0) {
a = Math.floor(x);
}
else {
a = Math.ceil(x);
}
return a;
}
function frac(x) {
//
// returns the fractional part of x as used in minimoon and minisun
//
var a;
a = x - Math.floor(x);
if (a < 0) a += 1;
return a;
}
//
// round rounds the number num to dp decimal places
// the second line is some C like jiggery pokery I
// found in an OReilly book which means if dp is null
// you get 2 decimal places.
//
function round(num, dp) {
// dp = (!dp ? 2: dp);
return Math.round (num * Math.pow(10, dp)) / Math.pow(10, dp);
}
function range(x) {
//
// returns an angle in degrees in the range 0 to 360
//
var a, b;
b = x / 360;
a = 360 * (b - ipart(b));
if (a < 0 ) {
a = a + 360
}
return a
}
function mjd(day, month, year, hour) {
//
// Takes the day, month, year and hours in the day and returns the
// modified julian day number defined as mjd = jd - 2400000.5
// checked OK for Greg era dates - 26th Dec 02
//
var a, b;
if (month <= 2) {
month = month + 12;
year = year - 1;
}
a = 10000.0 * year + 100.0 * month + day;
if (a <= 15821004.1) {
b = -2 * Math.floor((year + 4716)/4) - 1179;
}
else {
b = Math.floor(year/400) - Math.floor(year/100) + Math.floor(year/4);
}
a = 365.0 * year - 679004.0;
return (a + b + Math.floor(30.6001 * (month + 1)) + day + hour/24.0);
}
function caldat(mjd) {
//
// Takes mjd and returns the civil calendar date in Gregorian calendar
// as a string in format yyyymmdd.hhhh
// looks OK for Greg era dates - not good for earlier - 26th Dec 02
//
var calout;
var b, d, f, jd, jd0, c, e, day, month, year, hour;
jd = mjd + 2400000.5;
jd0 = Math.floor(jd + 0.5);
if (jd0 < 2299161.0) {
c = jd0 + 1524.0;
}
else {
b = Math.floor((jd0 - 1867216.25) / 36524.25);
c = jd0 + (b - Math.floor(b/4)) + 1525.0;
}
d = Math.floor((c - 122.1)/365.25);
e = 365.0 * d + Math.floor(d/4);
f = Math.floor(( c - e) / 30.6001);
day = Math.floor(c - e + 0.5) - Math.floor(30.6001 * f);
month = f - 1 - 12 * Math.floor(f/14);
year = d - 4715 - Math.floor((7 + month)/10);
hour = 24.0 * (jd + 0.5 - jd0);
hour = hrsmin(hour);
calout = round(year * 10000.0 + month * 100.0 + day + hour/10000, 4);
return calout + ""; //making sure calout is a string
}
function quad(ym, yz, yp) {
//
// finds the parabola throuh the three points (-1,ym), (0,yz), (1, yp)
// and returns the coordinates of the max/min (if any) xe, ye
// the values of x where the parabola crosses zero (roots of the quadratic)
// and the number of roots (0, 1 or 2) within the interval [-1, 1]
//
// well, this routine is producing sensible answers
//
// results passed as array [nz, z1, z2, xe, ye]
//
var nz, a, b, c, dis, dx, xe, ye, z1, z2, nz;
var quadout = new Array;
nz = 0;
a = 0.5 * (ym + yp) - yz;
b = 0.5 * (yp - ym);
c = yz;
xe = -b / (2 * a);
ye = (a * xe + b) * xe + c;
dis = b * b - 4.0 * a * c;
if (dis > 0) {
dx = 0.5 * Math.sqrt(dis) / Math.abs(a);
z1 = xe - dx;
z2 = xe + dx;
if (Math.abs(z1) <= 1.0) nz += 1;
if (Math.abs(z2) <= 1.0) nz += 1;
if (z1 < -1.0) z1 = z2;
}
quadout[0] = nz;
quadout[1] = z1;
quadout[2] = z2;
quadout[3] = xe;
quadout[4] = ye;
return quadout;
}
function lmst(mjd, glong) {
//
// Takes the mjd and the longitude (west negative) and then returns
// the local sidereal time in hours. Im using Meeus formula 11.4
// instead of messing about with UTo and so on
//
var lst, t, d;
d = mjd - 51544.5
t = d / 36525.0;
lst = range(280.46061837 + 360.98564736629 * d + 0.000387933 *t*t - t*t*t / 38710000);
return (lst/15.0 + glong/15);
}
function minisun(t) {
//
// returns the ra and dec of the Sun in an array called suneq[]
// in decimal hours, degs referred to the equinox of date and using
// obliquity of the ecliptic at J2000.0 (small error for +- 100 yrs)
// takes t centuries since J2000.0. Claimed good to 1 arcmin
//
var p2 = 6.283185307, coseps = 0.91748, sineps = 0.39778;
var L, M, DL, SL, X, Y, Z, RHO, ra, dec;
var suneq = new Array;
M = p2 * frac(0.993133 + 99.997361 * t);
DL = 6893.0 * Math.sin(M) + 72.0 * Math.sin(2 * M);
L = p2 * frac(0.7859453 + M / p2 + (6191.2 * t + DL)/1296000);
SL = Math.sin(L);
X = Math.cos(L);
Y = coseps * SL;
Z = sineps * SL;
RHO = Math.sqrt(1 - Z * Z);
dec = (360.0 / p2) * Math.atan(Z / RHO);
ra = (48.0 / p2) * Math.atan(Y / (X + RHO));
if (ra <0 ) ra += 24;
suneq[1] = dec;
suneq[2] = ra;
return suneq;
}
function minimoon(t) {
//
// takes t and returns the geocentric ra and dec in an array mooneq
// claimed good to 5' (angle) in ra and 1' in dec
// tallies with another approximate method and with ICE for a couple of dates
//
var p2 = 6.283185307, arc = 206264.8062, coseps = 0.91748, sineps = 0.39778;
var L0, L, LS, F, D, H, S, N, DL, CB, L_moon, B_moon, V, W, X, Y, Z, RHO;
var mooneq = new Array;
L0 = frac(0.606433 + 1336.855225 * t); // mean longitude of moon
L = p2 * frac(0.374897 + 1325.552410 * t) //mean anomaly of Moon
LS = p2 * frac(0.993133 + 99.997361 * t); //mean anomaly of Sun
D = p2 * frac(0.827361 + 1236.853086 * t); //difference in longitude of moon and sun
F = p2 * frac(0.259086 + 1342.227825 * t); //mean argument of latitude
// corrections to mean longitude in arcsec
DL = 22640 * Math.sin(L)
DL += -4586 * Math.sin(L - 2*D);
DL += +2370 * Math.sin(2*D);
DL += +769 * Math.sin(2*L);
DL += -668 * Math.sin(LS);
DL += -412 * Math.sin(2*F);
DL += -212 * Math.sin(2*L - 2*D);
DL += -206 * Math.sin(L + LS - 2*D);
DL += +192 * Math.sin(L + 2*D);
DL += -165 * Math.sin(LS - 2*D);
DL += -125 * Math.sin(D);
DL += -110 * Math.sin(L + LS);
DL += +148 * Math.sin(L - LS);
DL += -55 * Math.sin(2*F - 2*D);
// simplified form of the latitude terms
S = F + (DL + 412 * Math.sin(2*F) + 541* Math.sin(LS)) / arc;
H = F - 2*D;
N = -526 * Math.sin(H);
N += +44 * Math.sin(L + H);
N += -31 * Math.sin(-L + H);
N += -23 * Math.sin(LS + H);
N += +11 * Math.sin(-LS + H);
N += -25 * Math.sin(-2*L + F);
N += +21 * Math.sin(-L + F);
// ecliptic long and lat of Moon in rads
L_moon = p2 * frac(L0 + DL / 1296000);
B_moon = (18520.0 * Math.sin(S) + N) /arc;
// equatorial coord conversion - note fixed obliquity
CB = Math.cos(B_moon);
X = CB * Math.cos(L_moon);
V = CB * Math.sin(L_moon);
W = Math.sin(B_moon);
Y = coseps * V - sineps * W;
Z = sineps * V + coseps * W
RHO = Math.sqrt(1.0 - Z*Z);
dec = (360.0 / p2) * Math.atan(Z / RHO);
ra = (48.0 / p2) * Math.atan(Y / (X + RHO));
if (ra <0 ) ra += 24;
mooneq[1] = dec;
mooneq[2] = ra;
return mooneq;
}
function sin_alt(iobj, mjd0, hour, glong, cglat, sglat) {
//
// this rather mickey mouse function takes a lot of
// arguments and then returns the sine of the altitude of
// the object labelled by iobj. iobj = 1 is moon, iobj = 2 is sun
//
var mjd, t, ra, dec, tau, salt, rads = 0.0174532925;
var objpos = new Array;
mjd = mjd0 + hour/24.0;
t = (mjd - 51544.5) / 36525.0;
if (iobj == 1) {
objpos = minimoon(t);
}
else {
objpos = minisun(t);
}
ra = objpos[2];
dec = objpos[1];
// hour angle of object
tau = 15.0 * (lmst(mjd, glong) - ra);
// sin(alt) of object using the conversion formulas
salt = sglat * Math.sin(rads*dec) + cglat * Math.cos(rads*dec) * Math.cos(rads*tau);
return salt;
}
function find_sun_and_twi_events_for_date(mjd, tz, glong, glat) {
//
// this is my attempt to encapsulate most of the program in a function
// then this function can be generalised to find all the Sun events.
//
//
var sglong, sglat, date, ym, yz, above, utrise, utset, j;
var yp, nz, rise, sett, hour, z1, z2, iobj, rads = 0.0174532925;
var quadout = new Array;
var sinho = new Array;
var always_up = " ****";
var always_down = " ....";
var outstring = "";
//
// Set up the array with the 4 values of sinho needed for the 4
// kinds of sun event
//
sinho[0] = Math.sin(rads * -0.833); //sunset upper limb simple refraction
sinho[1] = Math.sin(rads * -6.0); //civil twi
sinho[2] = Math.sin(rads * -12.0); //nautical twi
sinho[3] = Math.sin(rads * -18.0); //astro twi
sglat = Math.sin(rads * glat);
cglat = Math.cos(rads * glat);
date = mjd - tz/24;
//
// main loop takes each value of sinho in turn and finds the rise/set
// events associated with that altitude of the Sun
//
j = 0;
rise = false;
sett = false;
above = false;
hour = 1.0;
ym = sin_alt(2, date, hour - 1.0, glong, cglat, sglat) - sinho[j];
if (ym > 0.0) above = true;
//
// the while loop finds the sin(alt) for sets of three consecutive
// hours, and then tests for a single zero crossing in the interval
// or for two zero crossings in an interval or for a grazing event
// The flags rise and sett are set accordingly
//
while(hour < 25 && (sett == false || rise == false)) {
yz = sin_alt(2, date, hour, glong, cglat, sglat) - sinho[j];
yp = sin_alt(2, date, hour + 1.0, glong, cglat, sglat) - sinho[j];
quadout = quad(ym, yz, yp);
nz = quadout[0];
z1 = quadout[1];
z2 = quadout[2];
xe = quadout[3];
ye = quadout[4];
// case when one event is found in the interval
if (nz == 1) {
if (ym < 0.0) {
utrise = hour + z1;
rise = true;
}
else {
utset = hour + z1;
sett = true;
}
} // end of nz = 1 case
// case where two events are found in this interval
// (rare but whole reason we are not using simple iteration)
if (nz == 2) {
if (ye < 0.0) {
utrise = hour + z2;
utset = hour + z1;
}
else {
utrise = hour + z1;
utset = hour + z2;
}
} // end of nz = 2 case
// set up the next search interval
ym = yp;
hour += 2.0;
} // end of while loop
//
// now search has completed, we compile the string to pass back
// to the main loop. The string depends on several combinations
// of the above flag (always above or always below) and the rise
// and sett flags
//
out= {
rise: no_rs,
set: no_rs
};
if (rise == true) out.rise = hrsmin(utrise);
if (sett == true) out.set = hrsmin(utset);
return out;
}
function find_moonrise_set(mjd, tz, glong, glat) {
//
// Im using a separate function for moonrise/set to allow for different tabulations
// of moonrise and sun events ie weekly for sun and daily for moon. The logic of
// the function is identical to find_sun_and_twi_events_for_date()
//
var sglong, sglat, date, ym, yz, above, utrise, utset, j;
var yp, nz, rise, sett, hour, z1, z2, iobj, rads = 0.0174532925;
var quadout = new Array;
var sinho;
var always_up = " ****";
var always_down = " ....";
var outstring = "";
sinho = Math.sin(rads * 8/60); //moonrise taken as centre of moon at +8 arcmin
sglat = Math.sin(rads * glat);
cglat = Math.cos(rads * glat);
date = mjd - tz/24;
rise = false;
sett = false;
above = false;
hour = 1.0;
ym = sin_alt(1, date, hour - 1.0, glong, cglat, sglat) - sinho;
if (ym > 0.0) above = true;
while(hour < 25 && (sett == false || rise == false)) {
yz = sin_alt(1, date, hour, glong, cglat, sglat) - sinho;
yp = sin_alt(1, date, hour + 1.0, glong, cglat, sglat) - sinho;
quadout = quad(ym, yz, yp);
nz = quadout[0];
z1 = quadout[1];
z2 = quadout[2];
xe = quadout[3];
ye = quadout[4];
// case when one event is found in the interval
if (nz == 1) {
if (ym < 0.0) {
utrise = hour + z1;
rise = true;
}
else {
utset = hour + z1;
sett = true;
}
} // end of nz = 1 case
// case where two events are found in this interval
// (rare but whole reason we are not using simple iteration)
if (nz == 2) {
if (ye < 0.0) {
utrise = hour + z2;
utset = hour + z1;
}
else {
utrise = hour + z1;
utset = hour + z2;
}
}
// set up the next search interval
ym = yp;
hour += 2.0;
} // end of while loop
out= {
rise: no_rs,
set: no_rs
};
if (rise == true) out.rise = hrsmin(utrise);
if (sett == true) out.set = hrsmin(utset);
return out;
}