Congratulations, happenby, for giving an intelligent reply.
Perhaps Neil is talking about an astrolabe. Used from about the year 250 until the 16th century.
Astrolabe
From Wikipedia, the free encyclopedia
"An astrolabe (Greek: ?????????? astrolabos, "star-taker")[1] is an elaborate inclinometer, historically used by astronomers and navigators, to measure the inclined position in the sky of a celestial body, day or night. It can thus be used to identify stars or planets, to determine local latitude given local time and vice versa, to survey, or to triangulate. It was used in classical antiquity, the Islamic Golden Age,[2] the European Middle Ages and the Renaissance for all these purposes.
While the astrolabe is effective for determining latitude on land or calm seas, it is less reliable on the heaving deck of a ship in rough seas. The mariner's astrolabe was developed to solve that problem."
Astrolabes were highly accurate and were eventually joined with precision time pieces.
Information on the mariners astrolabe for rough seas is found here.
https://en.wikipedia.org/wiki/Mariner%27s_astrolabe
Wiki continues
"At first mechanical astronomical clocks were influenced by the astrolabe; in many ways they could be seen as clockwork astrolabes designed to produce a continual display of the current position of the sun, stars, and planets. For example, Richard of Wallingford's clock (c. 1330) consisted essentially of a star map rotating behind a fixed rete, similar to that of an astrolabe.[27]
Many astronomical clocks, such as the famous clock at Prague, use an astrolabe-style display, adopting a stereographic projection (see below) of the ecliptic plane."
The astrolabe was used to do the job of determining latitude but they were very challenging to use at sea, as you have indicated, making them accordingly inaccurate. This principle was further developed by an invention that occurred in the 18th century that enables its use even in adverse conditions with greater accuracy, and was improved over many decades, even centuries, to the point where now very effective and precise versions are made even today, to serve as backup tools when GPS systems fail to deliver. I am going to post one video that demonstrates in great detail how to use a particular version made in Germany, for example.
I'll give you another chance to guess the name of the device to which I refer, before I post some very instructive videos that cover how they are used by modern navigators at sea.
Now if you would like to ask me a question, with respect, I am more than happy to try to answer.
Okay, I'll ask you directly, if that's important to you:
What is the name of the instrument that mariners have been using for the past 6 centuries
Actually it has been more like the past 4 centuries, but the principle it's based on has been used much longer than that.
to determine their angular distance in the northern hemisphere from the equator?
No it is not important to me whether you ask me or not. The point, which you still don't get, is you need to change your attitude. You're clearly a very unhappy person.
The purpose of forums is not to compete to see who can make the nastiest remark to other people. It is to arrive at the truth.
I know what instrument you are talking about, but why do you want to know? Is it pivotal to accepting the flat earth for you?
Your incessant penchant to comment on your opinion of the happiness of your opponent is telling.
If you know what the instrument is, perhaps you can explain how it works.
What I would like to know is how you can explain its function, in your dream world.
That is, explain how it works when presuming there is no curved surface on the earth.
For example, how do you measure the angular distance from the equator if there is no such angle like on a "flat earth"?
The ball's in your court.
The horizon always appears perfectly flat 360 degrees around the observer regardless of altitude. All amateur balloon, rocket, plane and drone footage show a completely flat horizon over 20+ miles high. Only NASA and other government “space agencies” show curvature in their fake CGI photos/videos.
FAIL.True to form, you have again ignored my question and have attempted to change the subject.
Your answer about the horizon being flat, amateur balloon, rocket, NASA, CGI, etc., does not answer the question:
What device has been used for the past few centuries to determine latitude from the rolling deck of a ship at sea (which is what a sailor has to deal with)
and how does it work in your flat-earth model? In any event, thank you for not continuing to whine about how you think I must feel, because that makes you appear feminine, even while you complain that I reply to women not to men. If you want me to reply to you then you should try acting like a real man.
E.g., try acting like a man by
answering the question like a man, instead of trying to change the subject.