Quick Guide to the Online Light Curve Generator

Since its creation in May of 1999 the online light curve generator has been one of the most popular tools on the AAVSO web site. As of 03/18/2003, over 160,000 individual light curves have been plotted. However, throughout that time we have been adding new features to the program so here is a guide to some new features as well as hints for using it.

The Data

Let's begin by running through the origin of the data in the graphs. When plotting, the first database accessed is the AAVSO Validation file. This is where we check to make sure the star is in our observing program. Next, the AAVSO International Database is analyzed. This database usually includes observations submitted up to about 90 days earlier, give or take a month. Finally, the Quick Look file is scanned to include any observations submitted between the current date and when the International Database was last updated. Different metrics are used to try and speed up the searching of all this data. Right now the average light curves takes about 2 seconds to plot. Most of that time is eaten up by the CPU (a dual-CPU P4 running Linux). It is largely dependant on the popularity of that star, SS CYG can take up to 15 seconds to plot.

Interface

Now we will take a look at how you can configure the input. First, obviously, you have to choose the star and time period for which you would like a light curve. The star can be in either Harvard Designation or AAVSO Validation File format. The date can be either in JD or mm/dd/yyyy. Next, you need to decide what data you want to display. You can choose to ignore Quick Look data and also fainter thans to give a cleaner plot.

The Plot

To some people, presentation is equally as important as what data you analyze. For them we have the ability to customize how you would like your plots to look. By far the most popular feature of the program is the ability to highlight your own observations as a different color. By doing this you can see how your observations compare with others. Additionally, you can change just about every aesthetic parameter of the plot. You can change the colors of the positive observations and of the fainter than observations. You can also change the height and width of the graph along with deciding on whether to include a grid layout or not. Finally, you can choose the type of graph. Options include Points, Lines, Lines & Points, Dots, Impulses, and Boxes. Each type has its own strength and weakness. Play around and find the best plot for the graph you are making.

API

We have a mini-API for the light curve generator. If you are a software programmer (either professional or hobbyist) feel free to contact us about how to access it. All you have to know how to do is form an HTTP Post request with some special variables and you'll get a branded/custom output image. Xephem is a popular program that currently uses this API. Go to http://www.aavso.org/xephem/ for more information. Recently we have been working with the KStars project on an API for their software package.

Use of Data

The only thing we ask is that you do not use the data for any scientific purposes. The data comprising the light curves have not been evaluated, i.e., passed the strict quality control of the AAVSO. Thus, the light curves are "unevaluated" and may contain data that fall outside of the average magnitude for a given time and star. If you need official data on any star in the AAVSO International Database, please fill out our online Data Request Form. Some of our data is now available immediately so after submitting that form so you won't even have to wait for someone to e-mail it to you.

Stats & Hints

Speed: If you don't want data as recent as the last 3 months, ignore the Quick Look data and it may shave a few seconds from the plot time. If you only need a quick glance at the data, choose a smaller graph and it will lower the download time of the image. Also, plot stars in order of designation (either direct or inverse is fine) because a cacheing feature in the CGI script may speed up the plot time.

Resolution: If you are creating a plot with lots of observations, consider plotting with Dots instead of Points. Also consider increasing the size of the graph or ignoring fainter thans. Finally, use the magnitude limits to block out the extremes of the plot. All of these options will make it easier to pick out individual observations.

Official Data: Evaluated Data on over 300 LPVs is now available online immediately. All you have to do is fill out our online Data Request Form and it is automatically e-mailed to you. You should use this resource instead of the online light curve generator for official scientific research. Also, we will be glad to e-mail you a custom light curve of a star using only evaluated data.

Dates: You can use JD day fractions (2451738.1318, 2451738.6, etc.) in the date to take a look at stars with periods less than 1 day.

Interesting Stats as of 07/15/00: An average of 100 light curves are plotted per day. The top three stars plotted (with estimated number of plots) are: 1. SS CYG (1100) 2. OMI CET/MIRA (820) 3. R CRB (550). The vast majority of the plots are all over the database showing that our membership has a very wide interest in variables.

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