 Shortly after departure, the traveling twin sees the stay-at-home twin with no time delay.At arrival, the image in the ship screen shows the staying twin as he was 1 year after launch, because radio emitted from Earth 1 year after launch gets to the other star 4 years afterwards and meets the ship there.During this leg of the trip, the traveling twin sees his own clock advance 3 years and the clock in the screen advance 1 year, so it seems to advance at the normal rate, just 20 image seconds per ship minute.