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OpticalXpress a guide to choosing Binoculars, Spotting Scopes & Telescopes

If you are just starting bird watching you may be confused by all the available options of Binoculars and Telescopes so we will try and guide you through the maze.

Binoculars

Compacts - Your first decision is "compact" or "normal". A good normal binocular will always beat a good compact so the main reason to choose a compact is on weight and pocket ability. We would recommend only 7x or 8x rather than the 10x's in this size binocular. Prices range from £30 to £300. A good pair would cost around £99.

Normal Size - Binoculars are available in two types 'Porro prism' or 'Roof prism' The porro is the more traditional 'dog leg' shape, while the roof prism design gives a shape like two tubes. The Porro's tend to be cheaper but as they are easier to make they can be exceptional value. The roof's normally start well over £100 through the popular £250 to £300 range right up to the very best at £1000. To sum up Porro prism's can be best value, while Roof prism's are neater and can be the best.

Do not be persuaded to buy high powers or zooms. The brightness and field of view will be very poor and you can't hand hold them anyway! The best power would be 7x or 8x for general use, up to 10x or just possibly 12x for bird watching if you have a steady hand. A good starting binoculars would be a good quality 8x30 or 8x42. These give bright and easy viewing whilst not being too big, prices £80-£300.

Telescopes

Price, Size & Weight - In general smaller scopes of 60mm (the size of the front lens) are cheaper than the 80mm. Apart from price, 60mm scopes are smaller and lighter making them ideal if they are going to be carried very far. However a good 80mm will always beat a good 60mm especially in poor light conditions and the larger exit pupil will make them easier to use. Please bear in mind a tripod will have to be used and carried. Money spent on a good tripod is always worthwhile.

What Sort Of Magnification Do I Need - For most telescopes 20x to 30x eyepieces are the norm and a wide angle design is an advantage. Zooms of perhaps 20-60x are popular as they allow variable magnification and are now almost as good in quality as fixed magnification.

Straight Or Angled - A beginner will find a straight easier to use as you point the scope directly at the subject you are viewing. They are also easier to use in a hide. Angled scopes can be more comfortable to use, lower on the tripod and therefore more stable - and easier to look at birds or objects high up. They are also easier when people of different heights are using the scope.

APO & HD Glass - This is an optional feature offered on most high quality telescopes and can double the price. It is worthwhile for the keenest bird watchers or those who must have the best. The special glass can give improved optical performance under some circumstances.

Helpful hints on choosing binoculars

OpticalXpress- Tecnical Guide

It's worth outlining a few technical terms that will help you make an informed choice of binocular or telescope.

IMPORTANT - Safety Information
Never look at the Sun through binoculars, telescopes or any other optical equipment.

Magnification and Brightness.
Basic binocular specifications are identified by numbers, for example, 8x21. The first number tells you the magnification, so 8x makes a subject appear eight times closer.  If you are viewing small subjects at long distances, you will probably need a larger magnification and for subjects that are close range, you will probably find a smaller magnification better.  You should be aware that more powerful binoculars will magnify any unsteadiness when you are holding the instrument (shake), so choosing a smaller magnification may give an apparently sharper image than a larger magnification.  The second number indicates the diameter of the objective lens (that’s the large lens at the other end of the binoculars from the eyepiece).  Dividing the diameter of the objective lens by the magnification of the binoculars gives a measure of how bright the image will be (Brightness Index).  For example, an 8x21 binocular has a BI of 21/8 = 2.6.  In daylight, a BI of 2 to 3 is normally satisfactory, but in low light, a BI of around 5 or more (e.g. 8x40, 7x50) will be much better.

Field of View (Angle of View)
If you can see a wide area of the subject, it’s much easier to find the part of the subject you want to look at.  Generally, a more powerful binocular has a narrower field of view, but there are variations between models.  A good 8x binocular should have an angle of view of 6o or 7o or more, while a 12x model may offer as little as 4o or 5o.

Lens Coatings
All good binocular lenses are coated in order to reduce internal reflections and improve the image quality.  It’s possible to give even better viewing, for example, by the use of ruby coloured anti-UV coatings  which help to cut through haze, as well as protecting your eyes against the harmful effects of ultra violet light.  It should be noted that the ruby coating may not produce the exact colour of the subject, they often produce a "cold, blue" image.

BaK-4 Prisms
Some binoculars are constructed with BaK-4 prisms, which utilise a superior glass to provide brighter, clearer, sharper images than would be achieved with ‘ordinary’ prisms.

Long Eye Relief
If you wear spectacles, you may find long eye relief helpful, as it will allow you to view a subject in greater comfort, without pressing your glasses against the eyepieces. It’s also helpful for short sighted users.


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