Sun’s Celestial Navigation Aid and Tools: Synopsis of how to calculate the line of position

this website is recommended as a self-instruction website for beginners or for old celestial hands getting back in practice.

The skill of calculating a line of position (LOP) using the sextant and the sun is essential for celestial navigation, and our interactive worksheet simplifies the process.

The course is free and includes examples for every step to obtain your line of position.

I want to emphasize that the ‘La Rochelle Exercise‘ page, which will lead you to the interactive worksheet page, are the two fundamental cornerstone pages of this website.

Remember that starting and completing the La Rochelle exercise will take time and effort for beginners

## Sun’s Celestial Navigation Aid and Tools: What is a line of position (*LOP*) ?

A Line of Position *(LOP) *is a straight line marked on a nautical chart on which one is located somewhere, determined through the use of a sextant and pertinent calculations.

The main purpose of this website is to provide instructions and guidance on how to plot and calculate this line of position with the sun using the traditional method.

In summary, while a *Line of Position* indicates that the vessel’s location is somewhere along that line, it does not provide a precise fix on its location.

Accurate determination of a vessel’s position requires the intersections of at least two *LOP’s* !!

Take an initial observation with the sextant to measure the height of the sun above the horizon and calculate the first *LOP. *

Then take a second observation some time later when the sun moves from east to west and changes its azimuth angle. Calculate the second* LOP* and intersect these two lines to determine your position.

Of course, there are several other factors to take into account, such as the movement of the ship between the two lines of position . However, the most important purpose of this website is to calculate this simple LOP.

Sun’s Celestial Navigation Aid and Tools:

In conclusion, *LOP’s* are a fundamental part of celestial navigation, which has been used by mariners for centuries to determine their positions at sea when other means of navigation, like GPS, are unavailable or unreliable.

### Sun’s Celestial Navigation Aid and Tools: the main goal

Indeed, the main goal of this website is to provide information on how to calculate this LOP (Line of Position).

To summarize, this process involves transitioning from the observations made with the sextant to drawing a straight line on a map.

Finally, eight identical exercises are conducted in various oceans, in the Northern and Southern Hemispheres, and at different times of the year, with the Sun as the only celestial object.

These exercises *simulate* the application of the following tools:

- A sextant,

- The nautical almanac,

There is also the possibility to print the daily pages online for strictly personal use. See my nautical almanac section under “ESSENTIALS”.

- A watch,

- a scientific calculator

- Dead reckoning position

Sun’s Celestial Navigation Aid and Tools:

###### Navigational knowledge required

This course requires a minimum level of navigational knowledge.

Placing a geographical point on a map, drawing a course line, and measuring a distance in nautical miles.

###### The interactive worksheet

The course is based on the use of a scientific calculator and the worksheet for manual completing.

Free interactive worksheet accompanies manual completion, providing detailed theory and calculations guidance.

This interactive worksheet is the most importent tool of this website.

Sun’s Celestial Navigation Aid and Tools:

However, after completing the exercise titled ‘La Rochelle ’ there is a small fee for the correct answers to the seven remaining identical exercises presented in the celestial course.

Note that while working through the La Rochelle exercise, there are at least three similar exercises fully worked out.

The store listed in the menu offers worksheets containing the correct answers (PDF version) for the seven remaining exercises, available for purchase.

Sun’s Celestial Navigation Aid and Tools:

### Comments

Hence, in this course you will not find topics like stars, moon, planets, or detailed sextant description. My aim is to avoid the student with too much information.

In this course, I do not take for granted that you already know how to use the formulas. Instead, I provide an explanation of how to use them.

The method we use in this course is the Saint Marc Hilaire method, which is employed in navy schools worldwide.

We carry out these exercises at various times throughout the year, in different oceans located in the Northern and Southern Hemispheres.

You will also discover how to calculate a local apparent noon sight.

Moreover, you will learn how to plan your day for the interval between two Lines of Position (LOPs).

Sun’s Celestial Navigation Aid and Tools:

###### Additionally, the benefits of these exercises.

– Certainly, You will be able to obtain your position at sea!

– Obviously, it will be easier for you to clear your exams at the Merchant Navy school.

-Basically, you will find the same formulas for the Moon, stars, and planets, so this course is also interesting for the midshipmen in the naval academy.

In conclusion, the main goal should be to fully master the “La Rochelle” exercise, as doing so will make tackling the remaining exercises a more enjoyable experience.

Sun’s Celestial Navigation Aid and Tools:

Proposing an alternative approach to calculate your position at sea without the use of a scientific calculator, based on logarithm and azimuth tables

This section serves as an additional feature on my website, and I would like to emphasize:

I do not recommend starting with this particular method.

Here, I introduce an age-old celestial navigation technique involving logarithms.

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