Binoculars in Astronomy

If you are interested in serious binocular observation I would recommend:

'Discover the Night Sky Through Binoculars' by Stephen Tonkin.

For many years, the advice given to beginning amateur astronomers has been "Start with binoculars". 

Stephen Tonkin shows you why this is excellent advice and takes you on a year-long journey through the night sky visible from northern temperate latitudes.  At the end of the journey, you will have a sound basic knowledge of the sky and will have gathered useful snippets of astronomical information and miscellany along the way.

(Quotation courtesy Stephen Tonkin)

This is my personal recommendation.

I have no affiliation with Stephen and make no profit from his sales.

Any optical instrument will show you more than the naked eye, but some binoculars are much better than others.  As a general rule, to avoid disappointment, you should stick to recognised makes, recommended sizes, and avoid Zoom binoculars of any kind. 

A good pair of binoculars can cost hundreds, but there are many under £100 that will serve very nicely.  Remember, these are optical instruments and the better the qualtiy of the materials and manufacture, the more you will pay.  With binoculars, as with telescopes, you have to choose a good quality instrument. Stick to recommended brands and you won't go far wrong.

Please note that good binoculars are not cheap and poor binoculars are no good for astronomy. To avoid disappointment, generally speaking, you should avoid new binoculars under £60 and second hand under £20. (Of any size!)

Above: My Swift Ranger 10x50s.  I got them second hand for £25 and they have proved to be an excellent buy.  Hand held, they are not too heavy and give good star images.

The universally recommended size for astronomy applications is 10 x 50.  That is to say, they magnify 10x and the object lenses are 50mm in diameter.  These are big enough to show the faint objects you'll want to reach and yet still be light enough that holding them is not too exhausting.  The slightest strain in holding binoculars translates to hand shake, image wobble and loss of a couple of magnitudes in detectable stars!

Technically able to show magnitude 11.0 stars in coal black skies, 10x50s are large enough for many applications in astronomy.  In general magnitude 9.0 - 10.0 is more realistic as a limit. They will show many stars of the milky way and in clusters such as The Beehive, Pleiades, Hyades, Brocchi's Cluster (The Coathanger) and Coma Berenices.  There is not enough magnification in binoculars for us to need to compare resolution.  The magnification limit of a 50mm objective is around 200x, so our 10x magnification doesn't approach the resolution limit.

Bigger magnifications show up your hand wobble and are difficult to use effectively for more than a minute or two.  These larger instruments are usually used mounted on a tripod, or monopod, and would not be recommended for your first pair of binoculars for astronomy.  It goes without saying that a nice pair of 20x80 binoculars would be superb on the milky way, but for your first pair, stick to the 10x50 formula.

Smaller binoculars don't really collect enough light, although 8 x 40s can be a reasonable instrument if they are of good quality. 

Tiny bins of 6x30 or the small sporting binoculars, (eg 8x22s,) should not be used for serious astronomy.

WARNING:

Something to watch out for is red coated optics.

Generally these point to shoddy manufacturing methods and corner-cutting.  I've even read that they are a merely a marketing ploy to get people to 'impulse buy' because they 'look' brilliant!

<EG: The "I.R.Vision" binoculars on the left look reasonable when you use them in the daytime, but in comparison to the Swift Ranger 10x50s (above) they are very poor indeed on astronomical subjects, the fainter stars are smudged or invisible.  Worse still, they were the same price!  A little care in selecting your binoculars will pay dividends.

It is always a good idea to check astronomical user reviews online before you buy binoculars.  Just Google your prospective make and model and there will be opinions galore!

Read 'Discover the Night Sky Through Binoculars' by Stephen Tonkin.

Research good center focus porro-prism 10x50 binoculars to begin with

(Not roof prism for your first pair).

Choose some 10x50 porro prism binoculars in line with this guide's recommendations.

Do your online astronomer's binocular reviews research before buying.

DO NOT WEAR YOUR GLASSES when observing with binoculars - Use the binoculars to focus!

Enjoy the wonderful views of the universe using your binoculars.

Variable Stars: 

Here's a project that's ideal for binoculars.

Variable Stars brighten and fade over a period of time. It is interesting to follow the light curve and provides a good project over a number of days, weeks or even months.  This is a project that suits locations where cloud is an issue requiring a clear night only every so often and not necessarily on a specific night!

There are many types of variable star:

Eclipsing Binaries, Cepheid Variables, Algol Variables, Tau-Tauri, Irregular and Semi-irregular variables to name a few.  My 'beginner's  list' below contains four different types.

Using your unaided eye, and your 10x50 binoculars, (depending on the star) you can observe the difference in brightness by comparing to other nearby stars.

Here is a list that will get you started comprising brighter stars that can be easily found and followed in your 10x50s. All these stars are easily visible from the Northern hemisphere:

You can enlarge the constellation diagrams by clicking on them.

Mira: Omicron = ο Cetus                  

Mira has the largest range in this list by far and represents a great long term project.

Brightness Magnitude Range: 3.4 - 10.0 

Period: 332 days

Algol: Beta = β Perseus                    

Algol has the shortest period in this list and represents a great starter project, with visibility all year round above 50° N.

Brightness Magnitude Range: 2.1 - 3.4 

Period: 2.87 days

Beta Lyra: Beta = β Lyra

This star is easily found high overhead in northern summer, not far from the 0.0 magnitude star Vega. 

Brightness Magnitude Range: 3.3 - 4.4

Period: 12.9 days

Delta Cepheus: Delta = δ Cepheus

This star can be found all year long circling the northern celestial pole, with visibility all year round above 42° N.

Brightness Magnitude Range: 3.5 - 4.4

Period: 5.37 days

Eta Aquila: Eta = η Aquila

Another northern summer variable star, not far from Altair in Aquila, the Eagle.

Brightness Magnitude Range: 3.5 - 4.4

Period: 7.18 days

Betelgeuse: Alpha = α Orion 

A northern winter and spring constellation. The famous Betelgeuse in the shoulder of Orion. A red giant with problems!

Brightness Magnitude Range: 0.4 - 1.3

Period: Irregular.  Betelgeuse fluctuates in brightness in a noticeable range and does so without regular pulsations.