NavList:

Herman Dekker, you wrote:
"I ask this because the word contrary is more often used in celestial navigaton calculations and more understable for me."

Yes, certainly! Nothing wrong with it if the word works for you. That word "contrary" falls in the category of navigation "jargon" for most modern English-speakers. You have to be told what it implies because it's a bit obsolescent. In modern English, "contrary" sounds like an opposing "attitude". People are contrary. Opinions are contrary. It doesn't seem to fit as a description relative to compass directions. Of course once it's been explained, the jargon makes sense. That's the trouble with jargon... 

So what's a non-jargon alternative? "Different" names works for me. Labels of "N and S" or "S and N" are different. If that doesn't sound right or doesn't translate well for you, another alternative would be "opposite". If the hemispheres (North/South or sometimes East/West) are opposite then "do this", else "do that". In my descriptions of the calculation of "polar distance" in my "Celestial Navigation in the Age of Sail" classes, I describe the rule using the word "opposite". As a general rule, I try to avoid adding un-necessary "jargon" to the subject.

Sorry for taking two days to get back to you on this. Thursday was "Thanksgiving" here in the US so a "day of rest" for me. And Friday (yesterday) is my traditional "movie day" to start the Christmas season. :) 

Frank Reed