Observation Binoculars with Angled Eyepieces

A question from a reader wanting to know more about binoculars with angled eyepieces recently popped up in my inbox and which I thought would be well worth expanding on and covering here on BBR:

Answer

Thanks for your excellent question. As far as I am aware they do not have a specific name, but what I think you are referring to is what is essentially a subset of optics that are often most commonly and somewhat rather ambiguously called Observation binoculars.

Also known as binocular telescopes (especially the very high magnification versions), these usually giant binoculars are most usually designed for long distance observation, plane spotting and in particular for astronomy. This is especially true for those with the angled eyepieces as this design makes if far easier and more comfortable to point the view upwards towards the heavens:

Straight vs Angled Eyepieces

Apart from the obvious size difference, most giant astronomy binoculars look like your standard bin, however there are a small selection that like many telescopes and spotting scopes come with angled eyepieces. So why the difference and which is best?

Straight Through Eyepieces
Straight through "Observation binoculars" will perform best as a long range terrestrial binocular where your view will be not too far from the horizontal most of the time.

However that is not to say they can’t be very successfully be used for astronomy or for airplane spotting, you just need to get a little creative with your mounting or your position relative to them so as to make getting under them and viewing upwards comfortable.

Angled Eyepieces
Usually this angle is set at either 45° or 90° to the barrels and as you can see from the image to the right, basically this setup makes it a whole lot easier to look through them whilst the objectives are pointed upwards.

With a straight through design you have to get under the instrument to look upwards, which with a heavy giant bin can be either too difficult or impossible to do by hand or the tripod you use has to be very tall.

So it is for this reason, if your main use for them is either astronomy or aircraft spotting the best option is an angle eyepiece design, however on the downside, most of those available are premium grade and thus don’t come cheap.

Binocular Telescopes vs Single Eyepiece Telescopes

We look through both our eyes all the time and thus as anyone who has used standard binoculars and a spotting scope, it just feels more natural to have both your eyes open when glassing.

Two Eyes Better than One
Whist it is kind of obvious anyway, there are solid scientific reasons as to why using both your eyes is an advantage, especially when looking at distant objects through optics:

The light that goes through your optic and into your eye lands onto your retina. Your retina contains special photosensitive cells known as rods and cones. The job of these is to convert the light energy into electrical impulses that are then carried via the optic nerve to your brain which deciphers this and produces the image that you "see".

With both eyes delivering this information, your brain is able to make a better image because it can average out the messages and thus reduce "noise" from any inconsistencies or interference.

Thus with two eyes, your perception of colors and contrast is much improved and so not only are you able to better make out faint objects, but the resolution of the image that you see is also superior.

Two Objectives Better than One
Also remember that with two objective lenses, the optical device is also able to collect more light than a single barrel scope, which in turn also means sending more light to your eyes for a better quality and brighter image.

So if using both your eyes is better, why are single eyepiece spotting and telescopes so popular?

Whilst there are size and weight advantages to a single barrel and eyepiece design that may be important to some, the answer to this basically boils down to cost.

When you consider that a spotting scope or refractor telescope is basically half a binocular, you can already understand that due to using less materials, it will be cheaper to produce. Add to this the complexity and technical expertise in ensuring that the collimation is perfect, it is easy to appreciate that an equivalent quality binocular telescope will cost more to produce.

Indeed prices for double eyepiece observation binoculars start at around $800 / £700 and the very best telescope binoculars will put you back well over $3000 / £700. For a selection of what is available and where to buy, take a look at the section below on Angled Observation Binoculars.

Thus the lower cost of single eyepiece scopes has ensured their popularity.

Angled Observation Binoculars

Below are some details on a selection of the better known binocular telescopes and where possible I have provided links to online retailers in a number of countries to give you an idea of prices and where to buy:

Alternative Option: Binoviewers

If you already own a telescope and you still want two eyepieces but don’t want to buy new optics or if you are looking to save some money there is another option that can work out cheaper in some cases: a Binoviewer.

In many ways these are mechanically very similar to the eyepiece section on your standard pair of bins, but instead of having two objective lenses to collect the available light, a binoviewer collects the light from a single barrel that fits onto a scope where your normal eyepiece would go. Once again some of these can cost a lot of money, however there are also some more affordable options like the Celestron Stereo Binocular Viewer that I have read some really good reports on.

Other popular makes include the TS Optics Binoviewer, William Optics Binoviewer, the TeleVue Bino Vue, Denkmeier Binotron-27 Super System and the Gary Russell Binoviewers. For a better idea of what is available and the prices in your country, take a look at Where to Buy BinoViewers (especially check the Amazon & Ebay links).

Further Reading:

I hope that this has helped, below are some links to related articles that may also be of help/interest::

• Guide to Binoculars for Astronomy
• High Powered, Long Distance Viewing Binoculars
• Plane Spotting Binoculars