How are individual target stars imaged by the Kepler CCDs?
The star images are spread across a “postage stamp” of 30 pixels. By spreading the light across a set of pixels, Kepler captures all of the photons from a target star without a single pixel saturating (filling up), which would produce faulty data. A second reason for spreading the light across a “postage stamp” of pixels is to compensate for any spacecraft movement. By surrounding the image of the star with sufficient pixels, any tiny movement of the spacecraft will not push the star beyond its “postage stamp” and the mission scientists can be assured that the measurements are accurate.
