When I started searching for a sextant to buy, I was presented with two options. A plastic sextant, or a metal sextant. 

The metal ones were clearly more expensive than the plastic ones, which got me wondering. What exactly is the difference between them and does it justify the difference in price?

As there wasn’t a simple comparison online, I had to do the research myself.

The difference between a plastic and a metal sextant is its construction material. Metal sextants are generally more sturdy and maintain their accuracy better, but plastic sextants are generally more affordable. You can, however, get similar accuracy with both.

The key takeaway from the comparison is that a skilled user can get a similar accuracy with either type of sextant.

With both types, you need to ensure that you adjust it properly before taking sights so that you reduce the errors in the sextant itself. 

You can read my detailed article about adjusting a sextant to eliminate errors here: Sextant Errors And Corrections

The additional strength of the metal sextant means that in between taking sights, it is more likely to retain its adjustments, so it could be easier to correct each time you use it.

A metal frame also has advantages in terms of overall longevity of the instrument. Especially with heavy use, a metal sextant is likely to retain accuracy over a longer lifetime.

In terms of ease of use, both metal sextants and plastic sextants are the same. I find that the mirrors and the telescope have the biggest influence over ease of use. Metal and plastic models both come with a range of telescope and mirror options, so effectively both have “easier” and “harder” models to use, depending on your own personal preferences.

I came to the conclusion that the main difference between a plastic and a metal sextant is purely in terms of the investment you are willing to make. You can spend more on a metal sextant, and you will expect it to last longer.

It just comes down to how much you expect to use it. If you are planning heavy use, investing in a metal one makes sense. If you are learning for fun and only planning occasional use, a plastic one will produce the same results for a lower price.

Are metal sextants more expensive than plastic sextants?

Metal sextants are more expensive than plastic sextants because of the additional costs of manufacturing the metal components which make up the frame of the instrument.

There is no doubt that plastic is an easier material to mould, and consequently manufacture at scale.

When the instruments are in calibration, it is significantly cheaper to recast plastic sextants that do not meet the calibration required than it is to recast a metal instrument.

Even once they are cast, other aspects of the manufacturing process are more expensive for metal sextants than they are for plastic ones.

For example, you can consider the ease with which you can drill a hole through the frame. To drill through a metal frame requires more expensive drill bits and more expensive equipment because the material is tougher.

This additional expense, however, is countered by the fact that the properties that make the sextant harder to make are the same properties that give it its longer service life.

Metal sextants are more expensive to produce. The additional cost is passed to the purchaser through its more expensive retail price.

Are metal sextants more accurate than plastic sextants?

Both metal sextant and plastic sextants have the potential to achieve the same level of accuracy.

When you are taking sights, the accuracy of the sight is dependent on how well you have compensated for the errors in your sextant, as well as your skill as a navigator.

Both metal and plastic sextants give you the ability to compensate for all the adjustable errors, so in that respect, their expected accuracy is the same.

The difference comes when you plan to take sights quickly if you do not have time to complete a full set of adjustments beforehand.

A metal sextant, with its more sturdy construction, is more likely to retain the corrections from your previous sight.

Of course, over time all sextants will degrade and become more susceptible to non-correctable errors. The most obvious one would be the warping in the frame of the instrument.

A metal sextant is likely to suffer from these sort of errors less than a plastic sextant.

This leads us to conclude that over time, metal sextants will be more accurate than plastic sextants. If you are planning on using your sextant frequently for years to come, it would probably be worth investing in a metal one over a plastic one.

Are metal sextants easier to use than plastic sextants?

The difficulty in using a sextant is not dependent on its construction material. Metal sextants and plastic sextants are both very similar in terms of how easy they are to use.

Factors that affect the difficulty of use can apply to either plastic or metal sextants.

For example, I find a semi-silvered horizon mirror is more difficult to use than a 50/50 horizon mirror. Either mirror could be fitted to either sextant.

Similarly, a good telescope makes the instrument easier to use. You could have a good telescope on a plastic sextant just as easily as you could have a bad telescope on a metal sextant. 

Overall, if you are a beginner looking for an easy telescope to use, I would recommend a plastic sextant. Not because it is easier to use, but because it is less of an investment in case you happen to buy one that you, personally, find harder to use.

Do metal sextants last longer than plastic sextants?

Metal sextants generally last longer than plastic sextants, however in the real world the service life of your sextant depends more upon how well it is taken care of than it does on its construction material.

Clearly metal is a more durable material than plastic, so things made out of metal tend to last longer.

With sextants, however, a metal sextant that is treated poorly will become unserviceable a long time before a well looked after plastic model.

If everything else is equal, a metal sextant will last longer than a plastic sextant.

Should I buy a plastic sextant or a metal sextant?

When deciding whether you should buy a plastic sextant or a metal sextant, I always recommend you consider your budget, your experience and your expected use case.

If you are a beginner, I’ll always recommend a plastic sextant because it will let you learn the instrument and potentially make mistakes without having invested too much money.

Once you become proficient, you can still get great results with a plastic sextant, so there is no need to upgrade unless you want to.

If you already know how to use the instrument properly, and know how to take care of it, then I would recommend investing in a metal sextant.

A well-maintanted metal sextant will last you a lifetime, so it is worth investing in one when you are ready.

A skilled navigator will be able to get great results with either, so it is important to get the one that is best for your particular circumstances.