Cooke Triplet)</h2>

<p>The first lesson will be to input a known lens prescription
using the LENS INPUT mode. While you are performing this task, have
your User's Reference Manual open to the LENS section. Look up each
command in the User's Reference Manual as you enter it. The lens
prescription which we will be inputting is that of a Cooke Triplet
(U.S. Patent #2,453,260). This lens is the only lens in the lens
library when you first install the program. We will use this
prescription throughout this tutor