// JavaScript Document // Returns integer portion of x function trunc(x) { if (x < 0) return Math.ceil(x); else return Math.floor(x); } // Returns fractional portion of x function frac(x) { return Math.abs(x - trunc(x)); } // Converts x (degrees) into radians function radians(x) { return (Math.PI/180 * x); } // Converts x (radians) into degrees function degrees(x) { return (180/Math.PI * x); } // Normalizes x (degrees) between 0 and 360 function norm(x) { x = x % 360; if (x < 0) x += 360; return x; } // Provides an unambiguous version of atan(y/x) function invtan(y,x) { ap = degrees(Math.atan(y/x)); if (y > 0) { if (x > 0) { for (j=-360;j<=360;j+=180) { a = ap + j; if ((a >= 0) && (a < 90)) return a; } } else { for (j=-360;j<=360;j+=180) { a = ap + j; if ((a >= 90) && (a < 180)) return a; } } } else { if (x < 0) { for (j=-360;j<=360;j+=180) { a = ap + j; if ((a >= 180) && (a < 270)) return a; } } else { for (j=-360;j<=360;j+=180) { a = ap + j; if ((a >= 270) && (a < 360)) return a; } } } return ap; } // Validates form entry fields function validate() { if ((parseInt(document.form.TH.value) < 1) || (parseInt(document.form.TH.value) > 12)) { alert("Hour must be between 1 and 12"); return false; } if ((parseInt(document.form.TM.value) < 0) || (parseInt(document.form.TM.value) > 59)) { alert("Minute must be between 0 and 59"); return false; } if ((parseInt(document.form.TS.value) < 0) || (parseInt(document.form.TS.value) > 59)) { alert("Second must be between 0 and 59"); return false; } return true; } // Returns entered time in Universal Time format function getUT() { hr = parseFloat(document.form.TH.value) + 12 * parseFloat(document.form.TAMPM.options[document.form.TAMPM.selectedIndex].value); if (hr % 12 == 0) hr -= 12; min = parseFloat(document.form.TM.value); sec = parseFloat(document.form.TS.value); hr = hr + min/60 + sec/3600; if (parseFloat(document.form.TCS.options[document.form.TCS.selectedIndex].value) == 0) hr = hr - parseFloat(document.form.TC.value); else hr = hr + parseFloat(document.form.TC.value); return hr; } // Returns entered date in Julian Day format // Argument is for fraction of day function getJD(time) { year = parseFloat(document.form.DY.value); month = parseFloat(document.form.DM.options[document.form.DM.selectedIndex].value); date = parseFloat(document.form.DD.value); date = date + time/24; correction = false; if ((year > 1582) || ((year == 1582) && (month > 10)) || ((year == 1582) && (month == 10) && (day >= 15))) { correction = true; } if (month <= 2) { year--; month += 12; } if (correction) { A = trunc(year/100); B = 2 - A + trunc(A/4); } else B = 0; if (year < 0) C = trunc((365.25 * year) - 0.75); else C = trunc(365.25 * year); D = trunc(30.6001 * (month + 1)); return B + C + D + date + 1720994.5; } // Performs calculation for Moon's position function calculate() { if (validate()) { // // NOTE: Epoch used is 1990 January 0.0 // // Time calculations UT = getUT(); // Universal Time document.form.UT.value = UT; JD = getJD(UT); // Julian Day document.form.JD.value = JD; D = JD - 2447891.5; // Days since epoch document.form.D.value = D; T = (JD - 2415020)/36525; // Julian Century // Sun calculations eg = 279.403303; // Mean ecliptic longitude of Sun at epoch wg = 282.768422; // Ecliptic longitude of Sun at perigee at epoch e = 0.016713; // Eccentricity of Earth's orbit at epoch N = norm(360/365.242191 * D); Ms = norm(N + eg - wg); // Mean anomaly of Sun document.form.MS.value = Ms; Ec = 360/Math.PI * e * Math.sin(radians(Ms)); ls = norm(N + Ec + eg); // Longitude of Sun document.form.LS.value = ls; // Moon calculations l0 = 318.351648; // Mean longitude of Moon at epoch P0 = 36.340410; // Mean longitude of perigee at epoch N0 = 318.510107; // Mean longitude of node at epoch i = 5.145396; // Inclination of Moon's orbit l = norm(13.1763966*D + l0); // Mean longitude of Moon document.form.L.value = l; Mm = norm(l - 0.1114141*D - P0); // Mean anomaly of Moon document.form.MM.value = Mm; N = norm(N0 - 0.0529539*D); // Mean longitude of ascending node C = l - ls; Ev = 1.2739 * Math.sin(radians(2*C-Mm)); // Correction for evection Ae = 0.1858 * Math.sin(radians(Ms)); // Correction for annual equation A3 = 0.37 * Math.sin(radians(Ms)); // Third correction Mmp = norm(Mm + Ev - Ae - A3); // Corrected anomaly of Moon document.form.MMP.value = Mmp; Ec = 6.2886 * Math.sin(radians(Mmp)); // Correction for equation of the centre A4 = 0.214 * Math.sin(radians(2*Mmp)); // Fourth correction lp = norm(l + Ev + Ec - Ae + A4); // Corrected longitude of Moon document.form.LP.value = lp; V = 0.6583 * Math.sin(radians(2*(lp-ls))); // Variation lpp = norm(lp + V); // True orbital longitude of Moon document.form.LPP.value = lpp; Np = norm(N - 0.16*Math.sin(radians(Ms))); // Corrected longitude of node lm = invtan(Math.sin(radians(lpp-Np))*Math.cos(radians(i)),Math.cos(radians(lpp-Np))) + Np; // Ecliptic longitude of Moon document.form.LM.value = lm; bm = norm(degrees(Math.asin(Math.sin(radians(lpp-Np)) * Math.sin(radians(i))))); // Ecliptic latitude of Moon document.form.BM.value = bm; e = (23+26/60+21.45/3600) - (46.815/3600)*T - (0.0006/3600)*T*T + (0.00181/3600)*T*T*T; // Obliquity of the ecliptic ra = invtan(Math.sin(radians(lm))*Math.cos(radians(e)) - Math.tan(radians(bm))*Math.sin(radians(e)),Math.cos(radians(lm))); // R.A. of Moon ra /= 15; // Convert from degrees to hours rah = trunc(ra); ram = trunc(frac(ra) * 60); ras = trunc(frac(frac(ra) * 60) * 60); document.form.RAH.value = rah; document.form.RAM.value = ram; document.form.RAS.value = ras; dec = norm(degrees(Math.asin(Math.sin(radians(bm))*Math.cos(radians(e)) + Math.cos(radians(bm))*Math.sin(radians(e))*Math.sin(radians(lm))))); // Dec. of Moon if (dec > 90) dec -= 360; decd = trunc(dec); decm = trunc(frac(dec) * 60); decs = trunc(frac(frac(dec) * 60) * 60); document.form.DECD.value = decd; document.form.DECM.value = decm; document.form.DECS.value = decs; nak(ra,dec,e); } } // Perform Nakshatram calculation based on Moon's position function nak(ra,dec,e) { AngleBetEqAndEcliptic = e; FPAShift = 22.3488; StarsMalayalam = ["Ashwini (Aswathi)","Bharani","Krithika (Karthikai)","Rohini","Mrigasira (Magayiriyam)", "Thiruvathira (Athira)","Punarvasu (Punartham)","Pushya (Pooyam)","Aslesha (Ayilyam)","Magha (Makam)", "Purva Phalguni (Pooram)","Uttara Phalguni (Uthram)","Hasta (Atham)","Chitra (Chithira)","Swati (Chothy)", "Visakha (Visakam)","Anuradha (Anizham)","Jyestha (Triketta)","Moola (Moolam)","PurvaAshadha (Pooradam)", "UttaraAshadha (Uthradam)","Sravana (Thiruvonam)","Dhanishta (Avittam)","Satabhisha (Chathayam)", "PurvaBhadra (Pururuttathy)","UttaraBhadra (Uthrattathy)","Revathi"]; StarsEnglish = ["Sheratan (Beta Arietis)", "41 Arietis", "Pleiades (Nu Tauri)", "Aldebaran (Alpha Tauri)", "Heka", "Betelgeuse (Alpha Orionis)", "Pollux (Beta Geminorum)", "Asellus Australis (Delta Cancri)", "Acubens (Alpha Cancri)", "Regulus (Alpha Leonis)", "Zosma (Delta Leonis)", "Denebola (Beta Leonis)", "Algorab (Delta Corvi)", "Spica (Alpha Virginis)", "Arcturus (Alpha Bootis)", "Iota Librae", "Delta Scorpii", "Antares (Alpha Scorpii)", "Shaula (Lambda Scorpii)", "Kaus Media (Delta Sagittarii)", "Nunki (Sigma Sagittarii)", "Altair (Alpha Aquilae)", "Alpha Delphini", "Lambda Aquarii", "Markab (Alpha Pegasi)", "Alpheratz (Alpha Andromedae)", "Zeta Piscium"]; RA = radians(ra * 360/24); D = radians(dec); E = radians(AngleBetEqAndEcliptic); A = radians(360/27); R = Math.sin(D) * Math.sin(E) + Math.cos(D) * Math.cos(E) * Math.sin(RA); R = R / (Math.cos(D) * Math.cos(RA)); if (Math.cos(RA) * Math.cos(D) < 0) S = Math.PI; else S = 0; if (Math.abs(Math.cos(D) * Math.cos(RA)) > 0.00000001) L = Math.atan(R) + S; else L = Math.PI/2 + S; L = L - radians(FPAShift) + 10 * Math.PI; N = 270 + Math.floor(L/A); N = N % 27; document.form.NAL.value = StarsMalayalam[N]; document.form.NALE.value = StarsEnglish[N]; }