980182.fig.007
Figure 7: The combined image of 1200 guiding frames on 51 Peg, total exposure time 20 minutes. The bright image to the left is the position of the star as imaged through the beam splitter the fainter image to the right is the light spilled over the fiber entrance and reflected back onto the guider camera. Guiding is done exclusively at the brighter image. Aperture photometry of the combined frame is used to measure the amount of light lost, here 32%.