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

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

If you’re lucky enough to live close enough to one of the UKs shipping lanes and you want to watch those ships as they cruise by just on the edge of the horizon, then you’re going to need some pretty high powered binoculars. Alternatively, if you live in a place opposite one of Great Britain’s ports and you want to study the various ships that dock across the bay your optical requirements will be somewhat different. Whatever sort of ship you’re planning on watching, we have the right advice for you to make an informed decision when it comes to buying the perfect pair of binoculars.

Where Do You Intend To Watch Ships?

As we just said, where the ships are that you intend to be watching will have a great deal of influence on the type of binoculars you choose. We want you to get the best from your optical investment and that means identifying the way you’re going to use them.

The Best Binoculars For Viewing Ships On The Horizon

The horizon is on average around 3 miles (5k) out to sea. To successfully watch ships that far out to sea, you’re going to need high powered binoculars. Which means you are going to need at least 12x magnification which limits your choice quite considerably. Plus to be sure to see details on those ships you’ll probably need even higher powered binoculars maybe even 15x. With any binoculars with a magnification above 10x, you’ll experience a shaky, often blurred image.

Why Does The Image Blur Above 10x Magnification?

There’s only one reason that binoculars over 10x shake, and that is human physiology. If a fit young human was to hold a sheet of paper in their hand, extended straight out in front of their body, the arm holding the paper would shake. It’s a basic human trait and it’s perfectly normal. Holding binoculars (which weigh substantially more than a sheet of paper) out in front of your face will cause a slight shake in your arms.

That slight shake magnified 12x to 15x is going to be so obvious and apparent that the image you can see through the binocular lenses will be pretty much unrecognisable. So the blurry image is due to your arms shaking exaggerated by the high magnification. That’s why we always advise no more than 10x magnification for hand held binoculars.


It is possible to hold 15x magnification binoculars without them shaking for a short while, but eventually your arms will tire and shake. To combat this, binocular manufacturers add tripod connectors to high powered binoculars. Obviously if you’re not holding the binoculars you won’t pass the shake onto them. Using a tripod does limit your movement but it will allow you to see clearly through the lens at the ships on the horizon.

If the particular binoculars you choose don’t have a tripod connector, adaptors can be purchased for a reasonable cost. There is another alternative, Image Stabilised Binoculars.

Image Stabilised Binoculars

I S binoculars have technology crossed over from the camcorder industry to detect any movement and correct it by constantly updating the image to keep it clear. I S binoculars are at the pricier end of the optical scale but allow you to move freely to more than one static position.

To summarise to watch ships on the horizon through binoculars you’ll need;

  • High Magnification
  • A Tripod Or Other Support
  • Or Image Stabilised Binoculars

The Best Binoculars For Viewing Ships In Port

If the ships you would like to see in more detail are moored in port, your choice of binoculars is greatly improved. You have plenty of scope when it comes to magnification, in fact anything up to and including 10x will be good for ship watching. That’s as long as you intend standing on dry land to watch the ships, if you’re planning on watching ships from a boat, then that’s another story with a whole new list of requirements.

Assuming you’re going to be land based, then all of the usual requirements for binoculars like objective lens diameter, magnification, field of view, and all the other “normal” considerations will need to be addressed. For general usage, we always recommend binoculars with a magnification of anywhere between 7x to 10x, with as large an objective lens diameter as possible.

The Best Binoculars For Viewing Ships From A Boat

Due to the motion of the sea, using binoculars from a boat is a difficult task because of blurry images due to movement. That’s why any sailor or maritime official will tell you 7x is the highest magnification for “normal” binoculars for use on a boat. Maritime binoculars also need a large objective lens diameter to allow as much light into the binoculars as possible (more below). Of course I S binoculars were made for use on a boat, and the Navy have been using I S for years.

Marine binoculars fall into a category of their own but we’ll still cover them here to give you all you’ll need to make the best decision on the binoculars to watch ships that will suit you best.

Now we’ve outlined the 3 scenarios you’re likely to encounter for watching ships, let’s get into more detail. Starting with;

Long Distance Viewing Binoculars For Watching Ships On The Horizon 

As the horizon can be around 3 miles from the shore, to see any passing ships in any detail at all, you’ll need at least 10x magnification. In reality, 12x or 15x will be better but for either of those you’ll definitely need a tripod or support of some sort. Also a large objective lens diameter is going to be needed because the only way light can enter the binoculars is through the objective lens. 

The overall weight of the binoculars will also increase with the size of the objective lens. So there will always be a trade off between image brightness and the weight of the binoculars. However, as you increase the magnification, unless you increase the objective lens diameter you’ll get dark images due to the exit pupil (see below). 

 Image Stabilised or I S binoculars allow you to use high magnification without any shakiness, because the internal gyroscopic technology detects and corrects any movement in the image. You can get I S binoculars with a 20x magnification which would give you great views of far off ships.

Port Watching Binoculars

If you’re planning to watch ships from across the bay that are in port, a decent 8×32 pair will do great. You could go up to 10x magnification but you’d need to increase the objective lens diameter which in turn increases the weight. In all honesty, an 8×32 pair will be fine for watching ships either in port or coming into the harbour.

8×32 binoculars have an exit pupil of 4mm which will be fine in daylight and they’ll be small enough and light enough to carry comfortably. Be sure to get fully multi-coated (FMC) lenses to reduce glare and improve brightness, contrast and light transmission.

Marine Binoculars For Watching Ships

Marine binoculars are specially designed for use aboard a boat, they never have more than 7x magnification and they always have a large objective lens diameter (usually 50mm). These give a large exit pupil which is very useful on cloudy days, plus the low magnification helps to cut down on shaky images. 

Many marine binoculars have individual focus as opposed to centre focus but that’s for you to decide as both are available. Individual focus means you focus each lens individually which also means assuming you are the only person using them you’ll never need to focus them again. Individual focus binoculars have a dioptre on each ocular lens and once set, the binoculars will be in focus (above a certain distance) always. Whereas centre focus is like any other binoculars and will need focussing every time you use them.

What To Look For In Binoculars

We’ve been pretty fast and loose with our binocular terminology so far, so it’s time to explain what all those terms mean.

Magnification & Objective Lens And How To Find Them

The magnification and the objective lens diameter are the most mentioned features for any binoculars. The magnification tells us how large the image we will see through the lens, and the objective lens diameter determines many factors.

You will find a series of numbers stamped onto the body of the binoculars separated by the letter X. Something like 8×32, 7×25 or 10×50. The first number indicates the magnification level and the X represents times. So 8x indicates the image you will see through the lens of that particular pair of binoculars will be 8 times larger than with the naked eye. 

The next numbers indicate the diameter of the objective lens in millimeters. So in the 8×32 binoculars we have 8 times magnification with an objective lens diameter of 32mm. Binoculars are classified by the size of the objective lens diameter, and run as follows;

  • Compact Binoculars – Objective lens diameter of less than 30mm
  • Mid Size Binoculars – Objective lens diameter between 30 to 40mm
  • Full Size Binoculars – Objective lens diameter of greater than 40mm

The Field Of View (FoV)

The whole image that can be seen through the binocular lens, from left to right while looking straight ahead, is called the field of view. The wider the FoV the more you can see, so with a wide FoV you’ll be able to see the whole ship, not just the stem or the stern. Magnification directly affects the FoV, as the magnification increases, the FoV gets narrower.

Which Type Of Binoculars Are Best?

There are two types of binoculars, Porro prisms and roof prisms, they both have positives and negatives and without getting too technical below are the pros and cons of both types.

Porro Prism Binoculars

Pros Of Porro Prism BinocularsCons Of Porro Prism Binoculars
Cost less than comparable roof prismsEasy to damage (misalign the prisms)
Higher rate of light transmissionHeavy
Wide FoVBulky
Realistic 3D imageLarge
Harder to waterproof

Roof Prism Binoculars

Pros Of Roof Prism BinocularsCons Of Roof Prism Binoculars
Compact, easy to carry & conceal Higher production costs due to precision components. That cost is passed on the purchaser
Lightweight design Fractionally less image clarity except in top of the range models
More robust than Porros, due to prism arrangement less likely to get damagedNarrower FoV
Easier to fully waterproof
Higher magnifications

Eye Relief

The eye relief is basically the perfect distance between the ocular lens (the one closest to the eye) and your eye while still seeing the full FoV. The average eye relief is anywhere between 12 to 16mm. If you wear glasses you’ll probably need more distance to fit your glasses, which is known as long eye relief. Long eye relief is between 16 to 24mm.

Exit Pupil

If you turn a pair of binoculars towards the light at arms length, and look through the objective lens, the circle of light you can see is the exit pupil. It’s basically the beam of light that enters the binoculars and illuminates the image you are looking at. The exit pupil of the binoculars should closely match the size of our own pupil, which in daylight averages between 3 to 5mm.

To calculate the exit pupil, divide the diameter of the objective lens by the magnification. So the exit pupil of the 8×32 binoculars is 32÷8 which equals 4mm, which is right in the middle of the daylight average.

Eye Cups

The eye cups are the soft plastic or rubber cups that are attached to the edge of the ocular lenses and cushion your face. They are adjustable by either twisting or rolling up or down.

Waterproof Binoculars

Whatever you use binoculars for, living in the UK they should be waterproof, especially for use watching ships whether from land or at sea. There are various levels of waterproofing, all using an industry coding system. IPX6 will prevent any water entering the binoculars from splashing, raining etc from any angle. IPX7 will prevent any water entering even if they’re submerged in a metre of water for 30 minutes.

Fog Proofing

An absolute must as far as we’re concerned, fog proofing prevents the lenses from fogging up when sudden temperature changes occur. All it takes is a sudden downpour after a hot sunny spell (which is not rare in Great Britain) and the binoculars could be steamed up. To prevent this, binocular manufacturers purge all the air from the lens tubes and replace it with an inert gas that contains no moisture and so cannot steam up.

Dust Proof

Once the gas is sealed into the lens tubes, not only can it not escape,but no dust, or sand enter. On beaches or around ports etc there is often a lot of sand flying about in the wind, the smaller pieces could enter the lenses and cause problems but not if they are fog proof.

Protective Coatings

Binoculars are easy to damage if they are dropped or knocked about, the majority of top quality binocular brands supply their binoculars coated in a rubber or polycarbonate coating to protect them from accidental damage.

Light Transmission

Watching ships involves a lot of looking at water, to see better through binoculars you need good light transmission. The glass used to make the lenses and the prisms makes a big difference to the light transmission. 

BAK4 Glass

This is high precision optical glass used in the manufacture of the prisms on top quality binoculars. It has the lowest imperfections of any optical glass which improves light transmission.

BK7 Glass

This is also high precision optical glass but has slightly more imperfections than BAK4 glass and is commonly used in binoculars.

E D Glass

Extra low Dispersion glass is used to improve image quality and prevent colour fringing and haloing. 

Lens Coatings

There are lots of different lens coatings available for binoculars and they help to reduce glare and improve the light transmission. If you can go for fully multi-coated (FMC) lenses as these have had every lens fully coated inside and out with multiple layers of glare reducing coatings.


You are going to invest a substantial sum of money on your binoculars so you’d expect a decent warranty. Most reputable brands offer a lifetime limited warranty on their binoculars which means as long as you own them, and don’t deliberately damage them, the manufacturer will repair or replace them with no quibbles.

Frequently Asked Questions

What are 7×50 binoculars good for?

7×50 binoculars are traditionally used for marine binoculars. They have as high a magnification as they can without causing the image to shake, and enough light gathering through the large objective lens.

What binoculars do the Marines use?

The marines use 7×50 binoculars.