Eric D. Wertz

After having my AWS account compromised I decided to take all my stuff out of the cloud and go back to hosting my own server at home. I used to have an old Dell machine but I haven't had it running in a few years. I had planned to replace it with a Banana Pi single board computer but never got around to building a case for all of the hardware. Then I had the thought to get a recycled thin client computer, figuring they would be pretty cheap and I could install Linux on it like a regular PC. So I went on ebay and found this for $50:

A Dell Wyse 7010 Thin Client

I like the idea of re-purposing old hardware, and this little box would be a compact and 100% quiet server that I could sit on my desk and not be annoyed by constant fan whirring.

Here is a JavaScript function that calculates the civil twilight start/end and sunrise/sunset times for a given latitude, longitude, and unix timestamp. (Note: the timestamp is in seconds, so the result of Date.now() needs to be divided by 1000 for this to work properly.) I use this function along with IP geolocation to change the colors on the page as the visitor's day shifts from daylight to dark.

This code was adapted from the information provided here.

function calcSunset( lat, lon, timestamp )
{
    function fmod( f, d )
    {
        let i = Math.floor( f / d );
        return f - i * d;
    }

    function deg2rad( r )
    {
        return r * ( Math.PI / 180 );
    }

    function rad2deg( r )
    {
        return r * 180 / Math.PI;
    }

    let jDate = ( timestamp / 86400.0 ) + 2440587.5;

    let n = Math.round( ( jDate - 2451545 - 0.0009 ) - ( lon / 360 ) );
    let jp = 2451545 + 0.0009 + ( lon / 360 ) + n;
    let rjp = jp;
    let l = null;
    let jTrans = null;
    let M = null;
    for( let i = 0; i < 5; i++ )
    {
        M = fmod( 357.5291 + 0.98560028 * ( rjp - 2451545 ), 360 );
        let C = ( 1.9148 * Math.sin( deg2rad( M ) ) ) + ( 0.0200 * Math.sin( deg2rad( 2 * M ) ) ) + ( 0.0003 * Math.sin( deg2rad( 3 * M ) ) );
        l = fmod( M + 102.9372 + C + 180, 360 );
        jTrans = jp + ( 0.0053 * Math.sin( deg2rad( M ) ) ) - ( 0.0069 * Math.sin( deg2rad( 2 * l ) ) );

        rjp = jTrans;
    }

    let theta = rad2deg( Math.asin( Math.sin( deg2rad( l ) ) * Math.sin( deg2rad( 23.45 ) ) ) );
    let H = rad2deg( Math.acos( ( Math.sin( deg2rad( -0.83 ) ) - Math.sin( deg2rad( lat ) ) * Math.sin( deg2rad( theta ) ) ) / ( Math.cos( deg2rad( lat ) ) * Math.cos( deg2rad( theta ) ) ) ) );
    let jpp = 2451545 + 0.0009 + (( H + lon ) / 360 ) + n;

    let jSet =  jpp + ( 0.0053 * Math.sin( deg2rad( M ) ) ) - ( 0.0069 * Math.sin( deg2rad( 2 * l ) ) );
    let jRise = jTrans - ( jSet - jTrans );
    let sunset = ( jSet - 2440587.5 ) * 86400;
    let sunrise = ( jRise - 2440587.5 ) * 86400;

    H = rad2deg( Math.acos( ( Math.sin( deg2rad( -6.83 ) ) - Math.sin( deg2rad( lat ) ) * Math.sin( deg2rad( theta ) ) ) / ( Math.cos( deg2rad( lat ) ) * Math.cos( deg2rad( theta ) ) ) ) );
    jpp = 2451545 + 0.0009 + (( H + lon ) / 360 ) + n;
    jSet =  jpp + ( 0.0053 * Math.sin( deg2rad( M ) ) ) - ( 0.0069 * Math.sin( deg2rad( 2 * l ) ) );
    jRise = jTrans - ( jSet - jTrans );
    let eveningTwilight = ( jSet - 2440587.5 ) * 86400;
    let morningTwilight = ( jRise - 2440587.5 ) * 86400;

    return {
        morningTwilight: morningTwilight;
        sunrise: sunrise;
        sunset: sunset;
        eveningTwilight: eveningTwilight;
    };
}

Had to update my site and ended up rewriting the whole backend to simplify the blogging process. Now everything is hosted from a thin client (server?) sitting on my desk, and it's super easy to update. I'll do some more detailed write ups sometime in the future.

Also there is now a fun thing with the background colors too... they should change from light to dark based on where you are visiting from.

here is a cat picture