7 Tips To Use A Sextant Like A Pro

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Having spent most of my professional career learning navigational skills and techniques, I can honestly say that mastering the sextant was one of the most challenging.

Fortunately, it does not need to be that difficult for everyone.

To give you a head start, I have compiled a list of what I consider to be the most beneficial tips to help you use a sextant like a pro.

1. Learn the theory behind how the sextant works

Learning how the sextant works is not the same as learning how to use a sextant.

I mean that you literally need to learn the principles behind how the sextant actually works.

The sextant is a navigational instrument, designed to measure the angle between two objects.

It uses a set of mirrors so that you can superimpose the two objects over each other and read the angle off of the arc of the instrument.

Once you understand the principles behind how the sextant works, it becomes much easier to apply them in practice.

You can read a thorough article about how sextants work here: How Sextants Work: An Illustrated Guide

2. Become intimately familiar with your own sextant

You should be able to pick up your sextant and perform all of the major functions with your eyes closed.

micrometer and clamp of a sextant
The clamp and micrometer of a sextant will be easy to use with your eyes closed.

Clearly, you won’t be able to take sights like that, but you should be able to operate the clamp; turn the micrometer screw; locate the adjustment screws; and adjust the shades.

Make your sextant your friend and get a sense of how everything feels.

For example, I use a Davis Mk15 (available from Amazon), and I know that there is a little friction in its arm, which increases towards the extreme limit of its altitude.

I also know that the micrometer screw turns with just enough friction that it is easy to stop turning when you get it in the right place.

3. Pick up your sextant correctly

The first thing you will do every time you use your sextant is to pick it up out of its box.

hand picking up a sextant from its case
Learn to pick up your sextant to set yourself up for taking your sights accurately every time.

Reach in and gently grasp the frame of your sextant with your left hand, then lift it up so that you can take hold of its handle with your right hand.

Spend a few minutes practising lifting it in and.

You’ll gain confidence in holding your instrument, and it will set you up correctly for taking sights every time.

4. Plan all your sights in advance

The most accurate sights rely on taking your observations at a precise time.

Give yourself the best head start by planning out your sights in advance. Not only will you be able to take them at the optimum time, but you will also know that you won’t waste valuable time in working out what you are looking for.

Shooting your stars is only a small part of the entire process, but is the most crucial for getting an accurate position.

The more time-consuming part is completing the calculations afterwards. You can save a considerable amount of time if you have planned well in advance and only need to fill in the numbers after shooting your stars.

5. Correct your sextant before every use

The accuracy of your position fix relies on the accuracy of your sextant.

No sextant comes out of its box holding full accuracy. They always need to be corrected in some way.

I won’t go into detail about correcting a sextant in this article, but you can read about it if you are interested: Sextant Errors And Corrections

The best practice is to perform a complete set of corrections before every set of sights.

In the beginning, you will need to allow plenty of time, but as you get used to your instrument the process will become much faster.

Not only will it ensure that your sights are as accurate as possible, but it will also work towards building familiarity with your instrument.

6. Practise with your sextant during the day

It is a common misconception that a sextant can only be used at night. Sextants can be used during the day as well. 

A sextant can be used during the day for taking sun sights, moon sights, vertical sextant angles and horizontal sextant angles.

Each method has a different optimum time for taking the sights. I can’t go into full detail in this section, but if you are interested then this post will tell you more: What Is The Best Time To Use A Sextant?

The main takeaway is that it is perfectly possible to obtain a position fix using your sextant during the day, giving you a great opportunity to practise.

Practising during the day means that it is easier to see the instrument and get used to its operation. It is also a lot easier to see the objects you are using through the telescope.

The sun shows up a lot clearer than stars do.

Practise during the day, then when it comes to taking your sights in low light you will be much more confident.

Pro Tip: When using your sextant during the day, take extra care to use its shades correctly. Never look at the sun without using the correct shades.

7. Use your sextant like a telescope

My final, and most important piece of advice is to forget about using your sextant to navigate.

Pick it up at night and literally just use its telescope for looking at different stars.

When I first started using my sextant, the hardest thing was to find celestial bodies in the sky. Actually taking the readings was relatively easy in comparison.

I found the best way to practise was to just look through the sextant and attempt to identify different stars.

It let me get used to the weight of the instrument and get a sense of how it felt in my hands.

After practising with the telescope, I noticed a significant improvement in my ability to point it directly at the stars I wanted to measure.

The tips we have discussed in this post will help someone familiar with a sextant to use it confidently and professionally. If you are looking for more information and would like a full step-by-step guide, you should check out: How To Use A Sextant: A Step By Step Guide