Adding twilight durations to dawndusk.asp

[Jonas Grinde]

Hi!

While fiddling with the code in the fantastic dawndusk.asp to add the observatory-location in the newly added day/night-map, I gained some confidence in my scavenger-style coding and programming and decided to add some more features.
I've added a new column in the table: "Duration", between the dusk & dawn columns... Simply showing how long each of the different twilight's will last, in the hh:mm:ss format. So now you can see how many hours of astronomical darkness you'll have, without having to do the maths yourself (lazy I know.) Maybe it's overkill showing seconds, opinions? View image below to see the result:
dawnduskduration.jpg

I've modified quite a lot, so I guess it's easier to download my new dawndusk.asp instead of making all the changes yourself.
(Remember to make a backup-copy of the original dawndusk.asp in case my modifications screw things up(Beta-testers wanted))


Here's the code if you want to modify it yourselves... I marked the whole table as green as it's better to replace it as a whole, instead of breaking up every row with inserted additions, big chance of messing things up.

<%@LANGUAGE="JSCRIPT"%><%
//
//   Display sunset and sunrise times for the current evening current place
//
// 22-Aug-11  rab Adapted from .vbs script
//              Created to run in a tiddler instead of in the console
//              Tweaked the SysJulianDate slightly (see below)
// 23-Sep-11  rbd Part of standard ACP UI. Credit Berg!
// 21-Sep-12  rbd GEM:871 Incorporate Robert Wahlström's high latitude changes
// 02-Feb-13  esy updated to calculate the dusk and dawn for the
//                current Astronomical day. If past dawn it will
//                calculate the next instead (same as if it was past
//                local noon). Also, changed the calculator to be a
//                function, rather than a "printer".
// 02-Feb-13  rab limited  arccos test to be [-1 to +1] .
//                regression tested for mid-Winter high latitudes --> OK
//
// 05-Feb-14  Mod By Jonas Grinde to add durations of each twilight to the table
//                 and adding day/night map with observatory location marked


var RADIANS_MULTIPLE = 0.0174532925              // multiply by degrees to get radians


var        SUNSET = -0.833333 * RADIANS_MULTIPLE; // upper limb at horizon, includes refraction correction
var         CIVIL =      -6.0 * RADIANS_MULTIPLE; // need artificial illumination to read outside
var      NAUTICAL =     -12.0 * RADIANS_MULTIPLE; // navigation using sea horizon no longer possible
var       AMATEUR =     -15.0 * RADIANS_MULTIPLE; // dark enough for most astronomical observations
var  ASTRONOMICAL =     -18.0 * RADIANS_MULTIPLE; // sky is completely dark


var   JULIAN_HOUR = 0.0417              // 1 hour as a fraction of a Julian Day
var JULIAN_SECOND = 0.0000115741          // 1 second as a fraction of a Julian Day


var DAWN = true ; var DUSK = false;          // set some vars to make code cleaner for dawn or dusk
var TODAY = false ; var TOMORROW = true;


function cdiff(JulianStart, JulianEnd) {
    // Calculates the difference between two Julian Dates
    // and returns the result as hh:mm:ss


    var diff = JulianEnd - JulianStart;
    var msec = diff;
    var hh = Math.floor(msec / 1000 / 60 / 60);
    msec -= hh * 1000 * 60 * 60;
    var mm = Math.floor(msec / 1000 / 60);
    msec -= mm * 1000 * 60;
    var ss = Math.floor(msec / 1000);
    msec -= ss * 1000;
    TimeDiff = hh + "h" + mm + "m" + ss + "s";
    return TimeDiff;
}




function this_twilight(theta_S, dawn_or_dusk, next_day) {
    // takes the solar elevation angle in radians and returns the
    // twilight ends (dusk) or starts (dawn) during this "astronomical day".


    var KT = new ActiveXObject("Kepler.Ephemeris"); // Re-usable Earth ephem (reverse = Sun!)
    KT.BodyType = 0; KT.Number = 3;                // This is a Planet. Earth.


    var tvec = new ActiveXObject("NOVAS.PositionVector");        
    var latitude = Telescope.SiteLatitude * RADIANS_MULTIPLE; 


    var JD = Util.SysJulianDate;                    // Current UT; Start with tomorrow's date/Time
    var LOCAL_JD = JD - (Util.SysUTCOffset * JULIAN_HOUR) ;
    var LOCAL_JDN = Math.floor(LOCAL_JD);
    
    // Are we looking for a dawn or dsuk calculation?
    if (dawn_or_dusk)
    JD = LOCAL_JDN + 1;
    else
    JD = LOCAL_JDN;


    // similarly, this is here to do the next astronomical day if we
    // are already past dawn.
    if (next_day)
    JD = JD + 1;
    else
    JD = JD;


    var JDPrev = LOCAL_JDN;


    do {                          // Iterate through until we converge on a solution.
          var KA = KT.GetPositionAndVelocity(JD).toArray(); // Get Earth from Sun
        // Reverse cartesian vector for Sun from Earth
        tvec.x = -KA[0]; tvec.y = -KA[1]; tvec.z = -KA[2];


    // J2000 coordinates of Sun from Earth
        var right_ascension_sun = tvec.RightAscension;
        var declination_sun = tvec.Declination * RADIANS_MULTIPLE;


        var HA = (Math.sin(theta_S) - (Math.sin(latitude) * Math.sin(declination_sun))) /
             (Math.cos(latitude) * Math.cos(declination_sun));


        if (HA >-1.0 && HA <1.0) { 
            HA = Math.acos(HA) / RADIANS_MULTIPLE; // HA in degrees
        } else { 
                return "//N/A at this latitude//";        // a bust! no solution for this latitude for today or tomorrow.
        }


        if (dawn_or_dusk) HA = -HA;          // if for dawn, invert the position of the sun.
    
    var LMST = Util.Julian_GMST(JD) + (Telescope.SiteLongitude / 15.0);


        JD = JD + (((HA / 15.0) - Util.HourAngle12(right_ascension_sun, LMST)) / 24.0);
    
    if (Math.abs(JD - JDPrev) < JULIAN_SECOND) {
        break;                                // Convergence to ~1 second accuracy breaks out of while loop
    }


        JDPrev = JD;
    }  while(true);
    
    KT = null; tvec = null ;                  // Explicitly release these


    return new Date(Util.Julian_Date(JD));
}


if (Util.Julian_Date(Util.SysJulianDate) > this_twilight(SUNSET, DAWN, TODAY)) {
    Response.write("It's After Dawn!\n");
    Response.write("Here are the //coming// day's sunset and sunrise times for //" +  Prefs.SiteName + "//\n" );
    Response.write("|>|!Dusk" + "|!Duration|" + ">|!Dawn|");
    Response.write("\n| Sunset is| " + this_twilight(SUNSET, DUSK, TOMORROW) + " | " + cdiff(this_twilight(SUNSET, DUSK, TOMORROW), this_twilight(SUNSET, DAWN, TOMORROW)) + " |" + this_twilight(SUNSET, DAWN, TOMORROW) + " |is Sunrise |");
    Response.write("\n| Civil twilight ends| " + this_twilight(CIVIL, DUSK, TOMORROW) + " | " + cdiff(this_twilight(CIVIL, DUSK, TOMORROW), this_twilight(CIVIL, DAWN, TOMORROW)) + " |" + this_twilight(CIVIL, DAWN, TOMORROW) + " |begins Civil twilight |");
    Response.write("\n| Nautical twilight ends| " + this_twilight(NAUTICAL, DUSK, TOMORROW) + " | " + cdiff(this_twilight(NAUTICAL, DUSK, TOMORROW), this_twilight(NAUTICAL, DAWN, TOMORROW)) + " |" + this_twilight(NAUTICAL, DAWN, TOMORROW) + " |begins Nautical twilight |");
    Response.write("\n| Amateur twilight ends| " + this_twilight(AMATEUR, DUSK, TOMORROW) + " | " + cdiff(this_twilight(AMATEUR, DUSK, TOMORROW), this_twilight(AMATEUR, DAWN, TOMORROW)) + " |" + this_twilight(AMATEUR, DAWN, TOMORROW) + " |begins Amateur twilight |");
    Response.write("\n| Astronomical twilight ends| " + this_twilight(ASTRONOMICAL, DUSK, TOMORROW) + " | " + cdiff(this_twilight(ASTRONOMICAL, DUSK, TOMORROW), this_twilight(ASTRONOMICAL, DAWN, TOMORROW)) + " |" + this_twilight(ASTRONOMICAL, DAWN, TOMORROW) + " |begins Astronomical twilight |");
} else {
    Response.write("Here are //today's//  sunset and //tomorrow's// sunrise times for //" +  Prefs.SiteName + "//\n" );
    Response.write("|>|!Dusk" + "|!Duration|" + ">|!Dawn|");
    Response.write("\n| Sunset is| " + this_twilight(SUNSET, DUSK, TODAY) + " | " + cdiff(this_twilight(SUNSET, DUSK, TODAY), this_twilight(SUNSET, DAWN, TODAY)) + " |" + this_twilight(SUNSET, DAWN, TODAY) + " |is Sunrise |");
    Response.write("\n| Civil twilight ends| " + this_twilight(CIVIL, DUSK, TODAY) + " | " + cdiff(this_twilight(CIVIL, DUSK, TODAY), this_twilight(CIVIL, DAWN, TODAY)) + " |" + this_twilight(CIVIL, DAWN, TODAY) + " |begins Civil twilight |");
    Response.write("\n| Nautical twilight ends| " + this_twilight(NAUTICAL, DUSK, TODAY) + " | " + cdiff(this_twilight(NAUTICAL, DUSK, TODAY), this_twilight(NAUTICAL, DAWN, TODAY)) + " |" + this_twilight(NAUTICAL, DAWN, TODAY) + " |begins Nautical twilight |");
    Response.write("\n| Amateur twilight ends| " + this_twilight(AMATEUR, DUSK, TODAY) + " | " + cdiff(this_twilight(AMATEUR, DUSK, TODAY), this_twilight(AMATEUR, DAWN, TODAY)) + " |" + this_twilight(AMATEUR, DAWN, TODAY) + " |begins Amateur twilight |");
    Response.write("\n| Astronomical twilight ends| " + this_twilight(ASTRONOMICAL, DUSK, TODAY) + " | " + cdiff(this_twilight(ASTRONOMICAL, DUSK, TODAY), this_twilight(ASTRONOMICAL, DAWN, TODAY)) + " |" + this_twilight(ASTRONOMICAL, DAWN, TODAY) + " |begins Astronomical twilight |");
 }


Response.write("\n----\n");
    var MapX = (Math.round(-2+((Telescope.SiteLongitude+180)*(720/360))));
    var MapY = (Math.round(20+(((Telescope.SiteLatitude*-1)+90)*(360/180))));
    Response.Write("<html><style>");
    Response.Write(".marker{position:relative;left:" + MapX + "px;top:" + MapY + "px;z-index:10;border:0px;opacity:1.00;}");
    Response.Write(".map{position:relative;left:0px;top:0px;z-index:1;border:0px;}</style>");
    Response.Write("<div class='marker'><font color=red><b>*</b></font> " + Prefs.SiteName + "</div>");
    Response.Write("<div class='map'><IMG SRC=http://www.timeanddate.com/scripts/sunmap.php border=0></div></html>");    
Response.Write("//~~Contributed by Dick Berg, author of the [[ACP Reference Guide|http://solo.dc3.com/ar/ACPRefGuide.html]]~~//\n");
Response.Write("//^^Computational improvements by Robert Wahlstrom, Erik Young, Jeffrey Jongmans and Jonas Grinde^^//");

%>

Thanks for having a look!

Best Regards
Jonas Grinde
http://www.grinderphoto.se