# How did Carina (in Pirates of the Caribbean $5$) determine the longitude with chronometer?

At first, let me quote some dialogues from Pirates of the Caribbean $5$: Dead Men Tell No Tales.

In a scene when she wants to purchase a chronometer, she has accused that she is a witch, but she defends herself in this way: "No, I'm not. Am I a witch for having cataloged over 200 stars?"

Also in another scene when she accused to be a witch, she defends herself in this way "I'm an astronomer."

In a scene in the ship on the sea, Carina says:

"This chronometer keeps the exact time in London.
I'm using it to make an altitude measurement to determine longitude.
Only then will we find our exact spot at sea.
"

Following this scene, she says: "I'm not only an astronomer, I'm also a horologist."

so we can conclude that:

she is an astronomer and a horologist with facilities and possibilities of only a chronometer and a pen and a book(or notebook), and an astronomical table in that book or in her mind, with no other additional equipments.

But Captain Jack's crew look at her like fools! It seems that I am on the same side as Jack's fool crews! Also, the film emphasizes that Carina is a woman of science and an astronomer, and I believe that there is a scientific support behind this dialogue.

How did she measure the altitude and determine the longitude by use of the chronometer?

Following this video from the answer by @cgiovanardi, I have faced too many related videos on youtube, and finally, $\color{Green}{\text{I have found this short}}$ video $\color{Green}{\text{, which answer the question!}}$