"Let her do it, Greg; this is everybody’s show." Explained what I wanted: Mare Undarum was now in dark semi-lunar; Sun had set. Invisible boundary between sunlight and Luna’s shadow stretched over us, a precise locus. Ships passing through our sky would wink suddenly into view going west, blink out going east. Visible part of orbit would stretch from horizon to some point in sky. If eyeball team could spot both points, mark one by bearing, other by stars, and approximate time by counting seconds, Junior could start guessing orbit—two passes and Junior would know its period and something about shape of orbit. Then I would have some notion of when would be safe to use radar and radio, and catapult—did not want to loose a load with F.N. ship above horizon, could be radar-looking our way.