2 Measuring the brightness of your variable star

Now that you have saved your images in FITS format, the next step is to measure the brightness of the variable star. This is done using a technique known as aperture photometry in which the brightness of a star in the image is measured against the background of the image, and by using a non-variable reference star as a comparison.

In the following sections you will look at how this technique works and how to identify the correct stars in your images.