Analysis

 

Before you start imaging and analyzing your own data, we suggest you use one of our sample data sets to learn the steps for obtaining a raw instrument magnitude. Links to these data are contained in the “Starting Analysis” section of the tutorial.

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What is VStar?

VStar is a multi-platform, easy-to-use variable star data visualization and analysis tool. Data for a star can be read from the AAVSO database or from a text file of your own creation. It will plot the data on a light curve then you can choose to superimpose means data and error bars if you like. VStar can also create phase plots and perform basic period search functions, all of which make it a valuable tool for data analysis.

 

Launching VStar

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Because VStar uses Java Web Start ™ technology, you will always get the latest version whether you save the start-up icon to your desktop or launch the program directly. You will see a warning dialog box, similar to those presented by other Web-downloaded applications. Click the "Trust" button, in order to launch VStar. Please note that in order to run VStar, you need to have the Java Runtime Environment 1.6 or higher installed.  VStar should run on any operating system that supports Java.

 

Using VStar

The easiest way to obtain data to plot is by requesting it directly from the AAVSO International Database. To do this, click the “New Star from AAVSO Database…” button in the upper left corner of the VStar screen, then choose a star from the 10-star drop-down list or type in the name of another star from the AAVSO database. You can change the date range of the plot, use the default range (the last two years worth of data), or select “All data” by clicking the checkbox and hitting “OK”.

 

What Next?

The 5-Star Data Analysis Tutorial is now available for download from the Citizen Sky web site.  This document will introduce you to VStar as well as a few other tools on the Citizen Sky site. The tutorial will also introduce you to some of the concepts of basic data analysis. We recommend it as the first place to stop for those new to light curves and variable star data analysis.

There is limited help available in the VStar “Help” menu which you can see in the menu bar along the top of the screen.

Also, use our Data Analysis Online Forum to ask questions and get help from other users.

• Please feel free to send questions or suggestions to the developers via the VStar Team.
• VStar is the creation of lead developer David Benn with help from the VStar Team.
• VStar is made available under the Affero GNU Public License, which requires that the source code be made freely available. Click here to visit its Sourceforge site.
• Vstar uses the Apache Commons Math library for anova (F-test, p-value) algorithms.

 

 

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Important VStar resources can be found here:
http://www.citizensky.org/teams/vstar-software-development/important-vstar-resources

In addition, you can obtain information about libraries used by VStar here:
jcommon-1.0.16.jar (http://www.jfree.org/jcommon/)
jfreechart-1.0.13.jar (http://www.jfree.org/jfreechart/)
jlfgr-1_0.jar (http://java.sun.com/developer/techDocs/hi/repository/)
mysql-connector-java-5.1.10-bin.jar (http://dev.mysql.com/downloads/connector/j/5.1.html)

Now that you have obtained instrumental magnitudes for the variable and comparison stars the next step is to perform the analysis to get calibrated magnitudes.

Calibration Tutorials

Beginner
If you downloaded the Beginner data set, this is the tutorial for you. In this tutorial you will calculate calibrated Visual or V-magnitudes without any air mass correction. This method is suitable for comparison stars no more than 10 degrees away from the variable star and for zenith angles less than 35 degrees.
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Data that covers multiple observations over a period of time is often referred to as time series data. Analysis of variable star data usually involves time series analysis because the observations are of a single star and spread out over a long time span.

One of the key goals of Citizen Sky is to teach participants how to analyse data - either your own or data contributed by other participants. We have three main projects underway to do this:Read more

One of the components that makes this citizen science project unique is its focus on data analysis. Participants aren't asked to simply to collect data for scientists to analyse, but they can do the analysis themselves. This includes steps such as identifying a project/problem/goal, collecting data, performing quality control procedures on it, analysing it and communicating results to others.

The first stage of the project, until Fall of 2010, will be focused more on the data collection aspect and background information on the project. We will begin building out the data analysis section around the beginning of 2010.Read more