I'm writing a planetary motion simulator with the HTML5 canvas element and I want to put one or more layers of stars in the background. The user can click and drag the screen to navigate around the map as well as zoom in and out. The map is infinite; they could scroll forever in any direction. I'd like to have the background layer move more slowly than the foreground so as to give the illusion of depth.
How should I go about implementing this? Can I load an image file and tile it? Should I create an SVG image? Should I just use the CanvasRenderingContext2D.fill() to create the background? I'm trying to keep the game running as close to 60fps as possible.