Binoculars for Astronomical Observation

Dear Mark,

Thank you for your SMS inquiry on which binoculars and magnification to buy for star gazing.


Light-gathering, not magnification:

The highest magnification to choose is one not more than 10 X. The most important thing in buying a telescope or binoculars for astronomical observation is not the magnification, but their ability to gather faint lights light years away.


It is the ‘light gathering’ capacity of the binoculars that counts, and not the magnification as most people think, or erroneously brain-washed to think. Most people are impressed by ‘magnification’ but only those who knows how to choose for astronomical uses, look for the size of the objective lens, and never the power of the eyepieces


The distant galaxies and stars:

The stars and all other stellar objects are so far away that no matter how much magnification you try to increase, you can never magnify the stars, or even the planets large enough except the Moon to have any meaning. All you see is just a point of light, and nothing larger.


The exception:

The Moon which is the nearest heavenly body and has plenty of light, does magnification counts more than light. It is the only exception if you are only thinking of lunar observation with a pair of binoculars. Even small telescopes can enlarge the planets for their disc to be visible.

But this is not so for the far-off stars. You can never expect to see details on the stars even by attempting to magnify them with large telescopes. You see nothing but just a point of light – the bigger the lens diameter, the brighter the point of light. No disc can be seen on stars which are light years away.



Faint lights to gather:

What is important is the ability for binoculars as well as for telescopes to gather as much light as possible of the very faint and distant stars, galaxies and nebulae. For that, you need as large a lens diameter as possible. That is why the larger the lens or mirror sizes of the objective, even for huge astronomical telescopes in observatories, the better details with the telescope. If you can gather as much light as possible from the faint stars and other deep sky objects you would be able to see them better. This applies also for binoculars.


Best combination of objective diameter and magnification:

For hand held binoculars which no one can hold in their hands for very long if you want to look upwards into the sky? You will ‘break your neck and back’ at the same time if you stand in that position holding a pair of binoculars. The best lens size to choose for a 10 X magnification binoculars is a 50 mm lens diameter. This combination is the best.


My strong recommendation is a 10 X 50 mm (maximum magnification) or a 7 X 50 mm (for wider field and brightness). This is the best buy for binoculars for astronomical observation as well as for terrestrial uses like bird-watching, scenery enjoyment, and looking at far off objects like ships at sea.


Dilutes the light, magnifies hand movements:


Moreover, if you are thinking of using a pair of binoculars for astronomical use, any magnification higher than 10 times, not only ‘dilutes’ the limited available light from the stars by spreading it over a larger area through magnification, but the magnification itself also magnifies the hand movements as you hold the binoculars.

Thus you will find the stars or faint deep sky objects not only much dimmer but also ‘dancing’ with every beat of your heart and with every tiny movement of your hands. You see nothing but just star lights dancing to and fro, and zigzagging in your field of view. It is not much to see like that. It is no worth it.


Narrower and narrower the field of view:

Over and above that, you will find the angle of view also becomes narrower, and the higher the power, the narrower the field of view, making it harder and harder to locate an object. This is so unlike looking at terrestrial objects in the day time where available light is not a problem, and objects are large and much easier to locate.

Harder and harder to hold up:

Not only just that, but the higher the magnification the heavier the binoculars or telescope, and it is impossible to hold it up for too long


7 X 10 mm is the best:

The best selection to my mind and experience, is a 7 X 50 mm, and at maximum a 10 X 50 mm binoculars, but never higher than that. A 7 X 50 mm offers the best view. It has the widest field of view, it is the lightest, and much easier to hold with the hands, and at the same time, it gives the brightest image which is exactly what you want for astronomy where all the celestial objects are so very dim when they lie light years away.


Anything bigger or higher, you need a tripod stand to hold it up as it is not possible to hold the instrument with your hands for more than a few minutes while bending your neck and back backwards looking up at the same time.


Do not be tempted to buy anything ‘more powerful.’ The higher the magnification and the larger the objective lens, the heavier they will be. They will be so heavy you would not be able to hold them up with your hands for very long unless you have a tripod stand to support them.


The best (armchair) method:

But the best and most comfortable method to use binoculars to avoid neck-breaking observation into the sky is to use a reclining arm-chair. Just adjust the reclining chair flat or almost flat and lie down on it (supine position). There you are, you will be so comfortable without the need to bend your neck and back. You need just hold the binoculars with your hands while resting the arms on a pillow or on the arm rests.


It is as simple and comfortable as that. It is very cheap and restful too when looking upwards. Your whole body is already looking upwards into the sky. You will not have arm, neck and back aches. That way, you can hold them up for hours and do all your observations while still lying down. It is so comfortable and restful you might fall asleep on your arm-chair while mid-way through observation. But you can have an alarm clock to wake you up when a celestial object of interest is overhead or over the meridian.


Which brand to buy?

As to this question, there are now a number of binoculars made in China which are not bad. Their optics are good. I bought one myself from a scientific instrument company near my place here in Gombak. It cost me just RM 150 some 10 years ago. You can get a China-made one these days for less than RM 200. They are just as good as those Japanese branded models which may cost 5 times as much.


However, instead of buying a pair of binoculars for astronomy, you can buy a hand-held and very portable reflective astronomical telescope called ‘Astroscan’ from the United Sates. Its mirror is 6 inches which is not bad for amateur astronomers.


I would recommend that if you just have amateur astronomy in mind.


Wish you happy viewing.


lim ju boo

Founder, and First President
The Astronomical Society of Malaysia