Vern’s Weblog

I spent some time recently to create my own WordPress blog theme. I couldn’t resist using Dan Laszlo’s excellent mosaic of Long’s peak and comet McNaught from last January. Dan is a member of one of our local astronomy clubs NCAS in Fort Collins, CO. After the comet disappeared for us in the northern hemisphere a member of the Boulder club, Paul Robinson, determined that it might be possible to still observe the tail and in fact did so. Dan was the first to photograph the comets tail extending above the horizon.

I’ve updated the Aurora add-on for NASA’s World Wind. The recently released (Feb 14) version 1.4 of World Wind now monitors cache files and updates them if they are expired. The Aurora add-on needed only a minor change to expire the cache so it will retrieve the current Auroral PMAps from NOAA National Weather Service Space Environment Center. You can download the updated plugin from http://www.sec.noaa.gov/pmap/GEpmap/

This works although the Earth/LayerSet.xsd that comes with WW-1.4 should technically disallow the markup within an ImageLayer. Apparently the LayerSet.xsd is not current.

If you haven’t given it a try yet, you might consider giving NASA World Wind a spin or two. It is somewhat similar to GoogleEarth but doesn’t have the privacy issues involved with sending all your clicking habits to Google. World Wind is not Earthbound, you may visit other world’s such as Mars and the Moon. Both GoogleEarth and WorldWind are great applications, each has their own advantages and disadvantages.

Earlier this morning, I completed an overlay for the folks at the National Weather Service’s Space Environment Center. The overlay displays the auroral power influx as measured by NOAA POES satellites, which gives some indication of auroral activity. Current version doesn’t update automatically — I’ll add that shortly.

Information and links for downloading NASA World Wind is available from http://worldwind.arc.nasa.gov/

After you get World Wind installed, you may download the Aurora overlay from the National Weather Service Space Environment Center at http://www.sec.noaa.gov/pmap/GEpmap/

General information about auroras is available at http://www.sec.noaa.gov/pmap

The Julian Day utility provides routines that are useful when performing astronomical ephemeris computations or simple date arithmetic. The Julian Day or Julian Day Number is the continuous count of days since the year -4712. The JulianDay class implements the algorithms presented by Jean Meeus, Astronomical Algorithms, Willmann-Bell, Inc., 1998, pp 59-66. The following code example shows how to use JulianDay class to compute the Julian Day Number for a given date, compute the Gregorian calendar date for a given Julian Day Number, perform simple date arithmetic, calculate day of week from Julian Day Number, and use the utility to format a date for output.

The source code may be downloaded from JulianDay.zip. Simply unzip the file in your favorite directory and review the JulianDayExample.java located in the src/com/raben/examples directory. The JavaDoc for the JulianDay class and the source cross reference are available. If you have installed ant on your system, you can can compile the source and example by changing to the src directory and entering the command:
ant all.

To run the example, change to the dist directory and enter the command:
java -jar JulianDay.jar.

/*
* JulianDayExample.java
*
* Created on March 29, 2002, 12:57 PM
*/

package com.raben.example;
import com.raben.util.JulianDay;
/**
*
* @author Vern Raben
* @version 1.0
*/
public final class JulianDayExample {

public static void main(String[] args) {
/**
* To get the Julian Day for the current
* time, just call the constructor with
* no arguments
*/
JulianDay julianDay=new JulianDay();

// Print out the current JDN
System.out.println(”Current jdn is “+julianDay.getJDN());

// Calculate the Julian Day one week ago
julianDay.add(JulianDay.DATE,-7);
System.out.println(”JulianDay one week ago was ”
+julianDay.getJDN());

// Calculate Julian Day when Sputnik-1 was
// launched (Oct 4, 1957 at 19:26 UTC)
JulianDay sputJD=new JulianDay(1957,JulianDay.OCTOBER,4,19,26);
System.out.println(”Sputnik-1 was launched at JD ”
+sputJD.getJDN());

// What day of the week was it (0=SUNDAY,1=MONDAY,etc)
System.out.println(”Day of week was ”
+sputJD.get(JulianDay.DAY_OF_WEEK));

/**
* You may also specify the output date format according to
* java.text.SimpleDateFormat
* Note that this only works for dates after Jan 1970, prior to that
* the date will be printed in sql date format by default
* Also, the date is always UTC
*/
julianDay.setDateFormat(”yyyy-MM-dd HH:mm:ss”);
System.out.println(”Today is “+julianDay.getDateTimeStr()+” UTC”);

}

}