The use of a sextant requires a clear horizon and visible navigable stars or the moon (or the sun during the day), a nautical almanac, Bowditch tables and considerable calculations. Plus a single sight, especially during the day using the sun, would only render a line of position, not a fix. Multiple LOP's advanced over several hours would be needed to establish a fix (actual position).
During a scene when Tami and Richard are watching a sunset, Tami references Bob Ross when poking fun at Richard. However given her time traveling overseas from 78-83 this couldn't have been a pop reference she knew. See Bob Ross's Joy of Painting was in production from 1983-1994, Season 1 ran from Jan 11th - Mar 29th 1983 and Season 2 ran from Aug 31st - Nov 23 1983. The first season of The Joy of Painting aired on many PBS stations across the east coast, but the audience was small. It ended up moving to a new home on public television. This time, at WIPB in Muncie, Indiana. Their initial trip would take them back to her home in San Diego and be home by October. Given these factors it's highly unlikely anyone on that side of the world would have heard of a new (low viewership) show that was Broadcast by non-commercial public television stations.