pressing a button when the star was within each doubled line. The reticle's angle was readable by the AGC. The two reticle measurements determined the star's position in the AOT's field of view. By doing this procedure with two different stars, the computer could determine the craft's orientation.

The sun shade was added late in the program, in 1967, after tests and modeling determined that the astronauts might not be able to see stars on the lunar surface due to direct sun light or light scattered by near-by parts of the LM impinging