How To Choose Binoculars For Watching Sailing

How To Choose Binoculars For Watching Sailing (Best UK Guide)

If you’ve found this article it’s because you’re interested in buying a pair of binoculars for watching sailing. There are two ways to use binoculars to watch sailing, either with hand held binoculars or with binoculars supported by a tripod. The differences between the two are the magnification power and the size of the objective lens.


This is because there’s a limit to just how high a level of magnification you’ll be able to use with hand held binoculars. It’s all down to human physiology, the human arm can only work under tension for a limited period without shaking. Ordinarily that shake doesn’t make any difference but when holding binoculars with a high level of magnification, that shake is magnified to that level.


For this reason we recommend never using hand held binoculars with a higher level of magnification than 10x, for greater magnification (12x and above) we recommend using a tripod. When it comes to the objective lens diameter, the larger the better in terms of light gathering ability, but the larger the objective lens diameter the heavier the binoculars become.

Why Are Objective Lens Diameters So Important?

The diameter of the objective lens determines a few important features when it comes to binoculars. Firstly the brightness of the image, because the only way light can enter the binoculars (and brighten the image) is through the objective lens. So for a brighter image you need a large objective lens.

Binoculars sizes

The objective lens diameter also determines the size of the binoculars, 

  • Binoculars with an objective lens lower than 30mm are considered to be compact
  • Between 30 to 40mm are considered mid size 
  • Greater than 40mm are considered to be full size.

The magnification and the objective lens diameter tells us the exit pupil of the binoculars too.

Exit Pupil

The exit pupil is the beam of light that enters the binoculars through the objective lens. For us to see the image through the lens clearly, the exit pupil needs to be as close to our own pupil size as possible. The human pupil is between 2.5 to 5 mm depending on how bright the day is, and dilates as darkness approaches to around 7 mm. To calculate the exit pupil of binoculars just divide the objective lens diameter by the magnification and the answer will be the exit pupil in millimeters. 

For example a pair of binoculars with a magnification of 8 and an objective lens diameter of 32 (8×32) has an exit pupil of 4 because 32÷8=4.

What Are The Features Needed For Sailing Watching Binoculars?

When watching sailing there are a few factors that need to be accounted for, for instance  the binoculars will need;

  • To Focus Over Relatively Large Distances
  • Cover A Wide Area
  • Easy To Spot Boats
  • Work In Reasonably Bright Conditions
  • To Follow Fairly Slow Moving Craft (This takes into account the distance from the sailing boats you’ll be)
  • To Be Lightweight

So you’ll need a pair of binoculars that will be lightweight, have a wide field of view, easy to find and follow fairly large boats moving at relatively low speeds, in fairly bright conditions.

How Much Will A Pair Of Binoculars For Watching Sailing Cost?

The price you pay for your binoculars will be largely your own decision influenced by how far your budget can stretch and what level of importance you place on binoculars. Whatever you decide, please don’t go for a cheap and cheerful pair, the £10.00 to £20.00 range are really not much better than toys. If you take one useful piece of advice from this article, let it be that with binoculars you really do get what you pay for.

A decent pair of binoculars that can be used for watching sailing and other more general uses will cost you at least £90.00 and up to around £350.00. But these will last for many years and still be brand new (as long as you look after them). 

Field Of View

The Field of View (FoV) is the width of the image you can see through the binocular lenses. As you’ll be watching sailing boats that are usually spread over a large area, you’ll need as wide a FoV as possible. Now the FoV narrows as the magnification increases, so you’ll need a magnification that’s no greater than 10x (due to the shaky arms) but unless you have a relatively large objective lens diameter, you’ll have a narrow FoV. 

Depth Of View

The depth of view is the objects closer to you than the one you’re focussing on. As you focus on the far object, the ones nearer to you will lose their focus, this means you’ll need to constantly be refocusing everytime you choose to look at a different boat. Just like the FoV, the depth of view decreases as magnification increases.

Image Stability

If the image you see through the binoculars isn’t stable, it will appear blurry through the binocular lenses. This occurs whenever we hold something for any length of time but it appears worse under high magnification which is why we recommend no greater than 10x for hand held binoculars.

Sometimes though, the weight of the binoculars can be an advantage, because lightweight compact binoculars are sometimes too light and difficult to hold and therefore harder to keep still. Of course if you use a tripod or stand there will be no shake at all and higher magnification power can be comfortably used.

There are also image stabilised binoculars available but these do tend to be at the pricier end of the market, and some have waterproofing issues (you’d need to check the specs).

Clear Image Resolution

In general, the larger the objective lens diameter, the more resolute the image appears. The amount of resolution depends on how much magnification you intend to use. For magnification levels of between 7x to 10x and even up to 12x a 42mm objective lens diameter will usually provide enough resolution. The main reason for larger objective lens diameters have more to do with light gathering abilities than increased resolution.

Which Style Of Binoculars Are Best For Watching Sailing?

There are two main styles of binoculars depending on the prism arrangement used to magnify images, they are Roof prism and Porro prism. They both have good and bad characteristics so the ultimate choice will have to be yours, depending on your specific needs and requirements.

Roof Prism Binoculars

The overall design means that roof prism binoculars are smaller, lighter, and far more compact than a comparably sized Porro prism. Plus the design makes roof prisms easier to fully waterproof. As there are less internal parts, roof prisms also have less that can go wrong, there’s no chance of prism misalignment for example, which is a major problem in Porro prism binoculars.

However cheap roof prisms are usually optically inferior to Porros due to the phase coatings needed to correct image phase which is peculiar to the way roof prisms are designed. These Dielectric coatings are expensive but once applied they will never go out of phase and the prism design means they can never misalign either.

The cheaper end of the roof prism scale tends to either not have any P-coatings or it is of inferior quality which is why a good pair of roof prism binoculars cost more than comparable Porros. We advise that if budget is your biggest concern, go for a decent pair of Porro prism binoculars but remember they will never be fully waterproofed.

Porro Prism Binoculars

Porro prisms have a wider FoV and produce a stereoscopic image because the objective lenses are set further apart than roof prisms. They also cost less to produce and that reduced pricing is reflected in the purchase price. As they do cost less to produce, Porro prism binoculars usually have superior optical abilities (when the Prisms are aligned correctly). They are larger, bulkier and heavier than roof prisms due to the arrangement of the prisms.

As they have more internal parts, Porro prisms are easier to damage and almost impossible to fully waterproof. The first you would know of any prism misalignment would be when the eye strain and headaches begin. If prism misalignment did occur the cost involved in addressing the issue would be far better spent on a replacement pair of binoculars (possibly roof prisms).

To summarise, the best binoculars for watching sailing in an ideal world would be either an unbreakable Porro prism pair or a decent roof prism pair. As an unbreakable Porro prism doesn’t exist, we’d recommend a good quality pair of roof prism binoculars because they are;

  • Lighter
  • Smaller
  • Compact Design
  • Fully Waterproof
  • Fog Proof
  • Dust Proof
  • Easier To Carry
  • Unlikely To Break
  • More Robust By Design
  • Sleek Stylish Design

Better Light Transmission Gives Better Images

As we said earlier, the image quality and brightness are reliant on light, and the only light that can enter the binoculars comes through the objective lens. So to improve light transmission the manufacturers use top quality optical glass to make the prisms and the lenses. 

Binocular Prisms

This is top quality precision optical glass that’s used to make the  best binocular prisms. BAK4 glass has the least imperfections and gives the best light transmission. The most common glass used for binocular prisms is BK7 glass, this is still precision optical glass but has slightly more imperfections. 

Binocular Lenses

To improve light transmission even more ED glass is used to make the lenses. Extra-low Dispersion glass combats chromatic aberration which causes a colour ring around high-contrast objects through the lenses.  Look for either HD (high density) glass or ED (extra-low dispersion) glass for the best light transmission lenses.

Lens Coatings

To help with light transmission further, the lenses are coated with specialist paint which not only improves light transmission but also improves brightness, contrast and reduces glare. There are a number of different types of coatings available but we have found FMC (fully multi-coated) to be the best for watching sailing. FMC means every piece of the lenses inside and out have been fully coated in multiple layers for a more consistent coating. The water can cause a very strong glare so fully multi-coated lenses are definitely recommended.

Anti-Slip Coating

To prevent accidental damage due to dropping the binoculars many of the top brands cover their binoculars in a protective coating. Usually rubber or polycarbonate, these coatings not only protect the binoculars, they also help to prevent them slipping from your grip.

Should Binoculars For Watching Sailing Be Waterproof?

Living in the UK, we recommend all binoculars should be waterproof because once they get water inside, binoculars will never be the same. There are many levels of waterproofing but for general usage binoculars IPX6 will prevent any rainwater entering them at all from any angle.

IPX7 can withstand at least 30 minutes submerged in one metre of water without any ingress.

Fog Proof

There’s nothing worse than reaching for your binoculars only to find the lenses are fogged up due to a sudden change in temperature. To combat this, binocular manufacturers purge the air from the lens tubes and replace it with an inert gas (Usually nitrogen or argon). As these gasses contain no moisture, they cannot react with extreme temperature fluctuations.

Dust Proof

Once an inert gas has been sealed into the lens tubes of binoculars none can escape, and nothing else can enter either. This means no dust, no mould spores and no microbial debris either.

Marine Binoculars

If you’re planning to watch sailing from on board a boat, you might be considering marine binoculars. If you intend to use binoculars from a boat often, then it’s worth investing in marine binoculars. If you’re more likely to use binoculars from land then marine binoculars might be a step too far.

Marine binoculars don’t come cheap and have a very specific intended use. As they usually have a lower magnification (7x) than usually needed for regular binoculars, marine binoculars are not really as adaptable as regular binoculars although the 50mm diameter objective lens is great for allowing light to gather and illuminate the boats you’re watching.


The best binocular brands offer a warranty on their products. Some offer limited lifetime warranties. This means as long as you own the binoculars and don’t damage them deliberately, they will repair or replace them, no problem.

Frequently Asked Questions

Should binoculars for watching sailing be waterproof?

Although not strictly necessary, as long as you’re staying on dry land, we would recommend all binoculars are waterproof to prevent any water damage caused by heavy rain or even water splashes.

What does FMC lenses mean?

FMC or fully multi-coated lenses means all of the lenses have been fully coated inside and out with multiple layers of light transmission improving, glare reducing coatings.