<sect1 id="tool-aavso">

<sect1info>
<author>
<firstname>Aaron</firstname>
<surname>Price</surname>
<affiliation><address>
<email>aavso@aavso.org</email>
</address></affiliation>
</author>
</sect1info>

<title>AAVSO Light Curves</title>
<indexterm><primary>Tools</primary>
<secondary>AAVSO Lightcurve Generator</secondary>
</indexterm>

<screenshot>
<screeninfo>
The AAVSO Lightcurves Tool
</screeninfo>
<mediaobject>
  <imageobject>
    <imagedata fileref="aavso.png" format="PNG"/>
  </imageobject>
  <textobject>
    <phrase>AAVSO Lightcurves</phrase>
  </textobject>
</mediaobject>
</screenshot>

<sect2 id="aavso-intro">
<title>Introduction</title>
<para>
&kstars; can display light curves for variable stars from the observing 
program of the <ulink url="http://www.aavso.org">American Association 
of Variable Star Observers</ulink> (<abbrev>AAVSO</abbrev>).  This 
program monitors over 6,000 variable stars and consists of 10 million 
observations going back almost a century.  &kstars; downloads the very 
latest data directly from the <abbrev>AAVSO</abbrev> database via the 
Internet, so a network connection is required to use this tool.
</para>
<para>
To use the tool, select a variable star either by 
<firstterm>designation</firstterm> or name in the left panel, and 
set the start and end dates to be plotted.  In the right panel,
select the type of data that should be plotted (see below).  When you have 
made you selections, press the <guibutton>Retrieve Curve</guibutton>
button.  &kstars; will automatically connect to the AAVSO server, 
which will generate the lightcurve plot and send it to your computer for 
display.  A sample lightcurve plot is shown below:
</para>

<screenshot>
<screeninfo>
A Sample Lightcurve
</screeninfo>
<mediaobject>
  <imageobject>
    <imagedata fileref="lightcurve.png" format="PNG"/>
  </imageobject>
  <textobject>
    <phrase>Sample Lightcurve</phrase>
  </textobject>
</mediaobject>
</screenshot>

<para>
Please not these light curves should <emphasis>NEVER</emphasis> be used 
in research, papers, presentations, publications, &etc; They are only 
meant to be used as a source of info for &kstars;. They have not been 
validated and passed the <abbrev>AAVSO</abbrev>'s strict quality control 
measures. We will be glad to give you good raw data simply by requesting 
it at <ulink url="http://www.aavso.org/adata/onlinedata/">http://www.aavso.org/adata/onlinedata/</ulink>.
</para>
<!-- broken link in 4.7 -->
<para>
Specific questions about the data in the light curves can be sent to 
<email>aavso@aavso.org</email>. 
</para>
</sect2>

<sect2 id="aavso-about">
<title>About Variable Stars</title>
<para>
<firstterm>Variable stars</firstterm> are stars that change in 
brightness.  A <firstterm>light curve</firstterm> is a plot of a 
variable star's brightness over time. By looking at a light curve you 
can see how the star has behaved in the past and try to predict how it 
will behave in the future. Astronomers also use this data to model
astrophysical processes in the star. This important to help us 
understand how stars work.
</para>
</sect2>

<sect2 id="aavso-data">
<title>The Data</title>

<para>
Here is a summary of the various types of data available in the light 
curves:

<itemizedlist>  
<listitem><para><firstterm>Visual Observation</firstterm>: 
This is an observation of a variable star by an observer with a 
regular telescope.  It means that an observer saw the star at Y 
brightness on X date and time.</para></listitem>

<listitem><para><firstterm>Fainter than</firstterm>: 
Sometimes the star is too faint to be seen by the observer. When that 
happens, the observer reports the faintest star seen in the field.  
These are called <quote>fainter thans</quote> because the variable star 
was fainter than the brightness reported.</para></listitem>

<listitem><para><firstterm>Average</firstterm>: 
This is a computed running average of all the data reported. The 
<firstterm>bin</firstterm> number tells the computer how many days to 
use in each average calculation. This will need to be adjusted based on 
the frequency of observations. The error bars represent the 1 sigma 
standard deviation of error.</para></listitem>

<listitem><para><firstterm>CCDV</firstterm>: 
These are observations reported using a <abbrev>CCD</abbrev> with a 
Johnson <abbrev>V</abbrev> filter.  <abbrev>CCDV</abbrev> observations 
tend to be more accurate than visual (but not 
always).</para></listitem>

<listitem><para><firstterm>CCDB</firstterm>: 
<abbrev>CCD</abbrev> observations with a Johnson <abbrev>B</abbrev> 
filter.</para></listitem>

<listitem><para><firstterm>CCDI</firstterm>: 
<abbrev>CCD</abbrev> observations with a Cousins <abbrev>Ic</abbrev> 
filter.</para></listitem>

<listitem><para><firstterm>CCDR</firstterm>: 
<abbrev>CCD</abbrev> observations with a Cousins <abbrev>R</abbrev> 
filter.</para></listitem>

<listitem><para><firstterm>Discrepant Data</firstterm>: 
This is data that has been flagged by an <abbrev>AAVSO</abbrev> staff 
member as being discrepant following <abbrev>HQ</abbrev> rules for 
data validation. Contact <email>aavso@aavso.org</email> for more 
information.</para></listitem>

<listitem><para><firstterm>Dates</firstterm>: 
The observational database the light curves are based on is updated 
every 10 minutes so you can get data in near real-time. Right now 
light curve data is only available back to 1961, but this will likely 
be expanded further back in time in the future.</para></listitem>

</itemizedlist>
</para>
</sect2>

<sect2 id="aavso-update">
<title>Updating your local copy of Variable Stars</title>
<para>
The <abbrev>AAVSO</abbrev> publishes the <!-- broken link in 4.7 -->
<ulink url="http://www.aavso.org/valnam.txt">full list of variable
stars</ulink> in their monitoring program.  This file is updated 
monthly with newly discovered variable stars.  To sync the list that 
&kstars; uses with the <abbrev>AAVSO</abbrev> master list, click 
on the <guibutton>Update List</guibutton> button in the 
<abbrev>AAVSO</abbrev> dialog.  &kstars; will then attempt to 
connect to the <abbrev>AAVSO</abbrev> database and download the 
latest list.
</para>
<note>
<para>
The customized data stream provided by the AAVSO was implemented for 
&kstars; by Aaron Price.  Thank you, Aaron!
</para>
</note>
</sect2>
</sect1>

