The correct translation should be "Nú sér Ragnarr ok þat þeir sjá."
from Haukur's Old Norse for Beginners, exercise 3.4 of Lesson 5. But I
don't understand the use of "þat" in the sentence. At first thought I
believe it to be "hvat þeir sjá". This topic does not seem to have
been introduced yet in the tutorial (unless I missed it? always
possible). Can someone explain it?