2.Use the RSI ray for the upper marginal ray for field 2 to determine the obscurations i-&yH  
on surfaces 2 and 3 (Hint: look at the ray height on S5). These obscurations make a fB,_9K5i  
hole in the corrector to prevent the light from passing through the corrector lens K<J9~  
twice. S]{oPc[7  
@o.I