70-year star in Talmud confusing sailors? I don't know if this question is a good fit for here - it probably wants the non-existent "History of Astronomic Navigation SE", or maybe just "History SE" - but I'll start here:

As described in this article here by Dr Mario Livio:  The Talmud (an 1500-2000 year-old Jewish book of laws and traditions) describes how a Rabbi anticipated hs ship getting lost, because “There is a star that appears every 70 years and induces navigation errors.  I thought it might appear and cause us to go astray.”. 

Various theories are put forward to the identity of this star - with the 70-year period suggesting Halley's comet, although another theory posits that it was a variable star (see article for details).

My question is one that the article doesn't seem to address: How could a comet or a variable star confuse sailors? Comets don't even look like stars, so as long as they don't cover up the Pole Star or any other important navigational bodies why should they confuse sailors?
Comets can look like stars. Sometimes the outside of the coma and tail of the comet are too faint to see with the naked eye, and only the central part of the coma is bright enough to be seen. In this case the comet will appear like a (slightly fuzzy) star.  Look at the Great Nebula in Orion. It appears star-like, perhaps a little fuzzy.  Other clusters and nebulae were initially classified as "stars".

Moreover in the language of the first century AD (and until relatively recently) the word "star" meant "any heavenly light" and included comets, planets, and meteors. A navigator at that time would consider a comet to be just a "hairy star", while the learnéd debated whether comets were astronomical or meteorological stars.

At the time, many people also believed in "astrology" (the belief that the stars could have magical influences on life on Earth). It would seem quite reasonable, then, to think a star that appears every 70 years could affect navigation in mysterious ways.

As with many such ancient texts, the correct interpretation is probably lost. I'd consider it to be a parable: A man may be knowledgable and wise (as evidenced by his knowledge of the stars) but still be poor. I see no reason to try to identify the "star", no more that I would try to identify the farm in Isaiah 28. Trying to prove the story is "scientifically correct" seems to miss the point.