The four diagrams in Figure 3 amply illustrate how extremely sensitive the specific impacts on astronomy are to the detailed properties of the proposed system. Although the contours for KPNO and CTIO are similar in shape, they are shifted both north and south and east and west with respect to each other. This effect is the result of para]lax and is important for two reasons: 1. In those cases in which the contaminated zone crosses the meridian, at least half of the ideal observing zone (the region within %30° of the meridian) would be lost. The loss of one half of the available observing zone is equivalent to increasing the sky background by a factor of two. Therefore, the working group concluded that this would effectively mean that faint-object astronomy would be impossible within the declination band of the contaminated zone as seen from a particular observatory. 2. Because of the apparent position of the contaminated zones, as viewed from mid-latitude observatories, the zones will, for all practical -purposes, mark the southern boundary of faint object astronomy for northern hemisphere observatories. It will mark the northern boundary for southern hemisphere observatories.
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