Waterproof Binoculars
Using binoculars whilst on a boat makes waterproofing an issue. Cheap binoculars will let water in, and that will lead to ‘fogging’ and rapidly make them useless. The best will have efficient (guaranteed!) seals and have been ‘purged’ with nitrogen during manufacture to avoid any possible condensation inside.
These high-quality instruments will also be sheathed in rubber, giving them a degree of shock-proofing – handy if you plan to drop them in a boat or crunch them against the gunwales!
Porro or Roof Prisms
Porro Prism Binoculars
Traditional (chunky) binoculars have prisms that kick the light sideways to get the image right-way up. They are easier to make, and therefore always cheaper than the more complex alternative. Most porro prism binoculars "kick out" so the eyepieces are closer together than the objective lenses, but some are available that "kick in" to give a more compact shape – easier to hold.
Roof Prism Binoculars
The other way of achieving the same effect (image right way up), is rather more complicated – but gives binoculars with two parallel tubes (rather than a kink). These are more compact than porros, but inevitably more expensive than those with similar optical properties.
What Magnification to Choose
The more the binoculars magnify, the more the image will shake when you do – so anything more than X10 is effectively counterproductive. Given that the boat you are on will also be moving, about X7 or X8 is the usual recommendation. Zoom binoculars are available, but their complexity makes them much more expensive and adds weight.
Field of View
The wider the better. Wide angle binoculars will mean that you can watch more of the sea and therefore be more likely to catch the whales as they surface. Again this is something that you have to pay for.
Light Gathering
The diameter of the objective lens determines how much light is captured (7X50 is much brighter than 7X35). Given that whale watching is a daytime pursuit smaller objectives (giving lighter binoculars) are quite acceptable - typically 7X35 or 8X40.
Binoculars for Spectacle Wearers
Details of the eyepiece lens affect how far away from the eye binoculars work best. If you wear spectacles (eye-glasses) or sunglasses it is essential that the binoculars are comfortable to use with your glasses still in place – there will not be time to take off your glasses and fumble around as the whales flash past!
A Personal Choice
Binoculars need to be tried out before purchase – (if you can’t try – don’t buy!). Any good store will allow you to take a selection outside for testing. You have to try raising and focussing quickly, and imagine how they would feel after a few hours use. There is no ‘correct’ choice, but many people find that wide-angle 8X40 porros are good and cost-effective.
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