Often the question comes up about flat field images and what they are used for in astronomical image processing.  I've developed a short presentation to try and answer these questions.  It is not a presentation on how to apply the flats, but one that explains a little about how they are acquired and what effect they have on the actual CCD image.  Due to the image compression that is required to produce my presentation, the flat field images have a "bulls eye" appearance.  The "ring" nature of the displayed flat field image is not in the actual image.  The flat field image is a smooth image with no "rings".  Please keep this in mind while viewing the presentation.

My presentation is scaled for a browser resolution of 1024 X 768.  If you are using Internet Explorer for a browser, I suggest pressing F11 before starting the tutorial.  This will allow the browser window to show the tutorial without having to use the scroll bars.  For your convenience, the Play, Pause and Time Line slider at the bottom of the screen is active.  After the tutorial finishes, press F11 again to restore the browser display to normal and then use the back button to return to this page.