2.Use the RSI ray for the upper marginal ray for field 2 to determine the obscurations cZN<}n+q  
on surfaces 2 and 3 (Hint: look at the ray height on S5). These obscurations make a fGV'l__\\  
hole in the corrector to prevent the light from passing through the corrector lens u|wl;+.  
twice. =M?+KbTJ3  
-%J9!(  
3. Use a targeted ray for the negative full field to hit the edge of the obscuration on Y`22DFO  
surface 2 to determine the size of the obscuration on surface 1. This obscuration eMdP4<u  
prevents ghost images (prevents rays from going through the hole in the corrector uSXnf  
lens). SVVE