There is a lot of fun to be had observing the heavens with a pair of astronomy binoculars but it can be confusing which pair would work well for what you want. Just like any astronomy equipment, there are several things we need to discuss before we just right in.
When you are using binoculars in the daytime, the diameter of the lenses is not that big of a consideration. In astronomy however, the larger the diameter, the better you can see objects like nebulae and galaxies. The minimum you should consider is 50mm with the maximum being based on what you can comfortably hold (the larger the diameter, the heaver they are) and what you are willing to spend (larger usually means more expensive).
For hand holding, which is what we are talking about here mainly, you should stick between 50mm and 70mm. Smaller ones will make it harder to see objects and larger ones will make it harder to hold them steady enough to be useful.
Magnification is not as important but should be kept between 10x and 20x for most handheld applications. Less magnification means you will have a hard time seeing anything you want to see, whereas too much magnification will be hard to hold still enough to actually use them.
The most common starter size of astronomy binoculars is 10x50s and these are widely used in the field. For those wanting more, 15x70s is the next most popular size, primarily for those who forgo telescopes in favor of binoculars.
Optical quality matters
The quality of the optics not only makes objects clearer and sharper, it also increases the contrast between the object and the background of space.
If you were only looking at stars then contrast and sharpness would not really be much of an issue, but few people use astronomy binoculars for looking at nothing but stars.
Seeing nebulae and galaxies depends greatly on picking the very dim objects out from the slightly darker background. This makes increasing contrast a huge deal. In fact, if you read an astronomy or astrophotography book you will find that they often talk about adding filters to increase the contrast of what you are looking at. Adding filters to a pair of binoculars is not as easy as adding them to a telescope so you are better off getting high quality optics to start with.
Standard 10×50 general use binoculars
The Celestron 71198 Cometron 7×50 Binoculars are the perfect place to start if you are unsure about how much you will be using your new astronomy binoculars, just want to dip your toe into this hobby, or just need a pair to help you get your telescope pointed where it needs to be. They are also perfect for astronomy clubs or for kids as the price is low enough that should a pair get lost or damaged, no one is going to get upset.
With light weight, reasonable optics, and threads for a tripod adapter, it has all the boxes checked for a basic set of astronomy binoculars.
The next step up is the Orion 09332 Scenix 7×50 linear view Binoculars which have a wider field of view, better optics, and better eye relief (which is better for eyeglass wearers and future eyeglass wearers). If you are even remotely serious about viewing objects in the night sky or having your astronomy binoculars around for more than a couple years, this is the minimum I would recommend. They offer excellent features and should last for many years to come.
Views with these binoculars seem brighter and have better contrast than the Celestron model above helping you pick out faint whisps of dust around the Orion Nebula and much more.
These Nikon 7245 Action 10×50 EX Extreme Binoculars are what I consider the top of the line in astronomy binoculars even though there are far more expensive binoculars out here. More amateur astronomers and astrophotographers I know use these then any other model out there, including myself.
These are so popular because the optics are amazing, they are waterproof so dew will not affect them, they have padded rubber coatings to make them easy to hold on to and prevent dings should you drop them or bang them into something, they are smooth as glass to use, and they have a lifetime warranty. That’s right, lifetime warranty from one of the world’s premiere optics manufacturers.
Of course the Nikons have all the bells and whistles too such as very nice twist up eye cups, a very reasonable neck strap, diopter adjustments, threads for a tripod adapter and more.
Are there better 7×50 astronomy binoculars out there? Sure, but once you get better than the Nikons you spend a lot of money for not a lot of gain, which is why these are the ones most people I know use.
Larger astronomy binoculars
Once again we start out with Celestron and their Celestron SkyMaster Giant 15×70 Binoculars. It is hard to beat their combination of reasonable quality with extreme affordability. While certainly not top of the line, these provide substantially brighter images and a little more magnification than their 10×50 model discussed above. They do this while only only increasing the price by about $30, and that is no easy feat as you will see shortly.
While I would not really want a pair of these for serious use, they are more than acceptable for someone just starting out or as loaners for an astronomy club.
Next up we have a little of a hidden jem, the Orion 09466 Mini Giant 15 x 63 Astronomy Binoculars. These are a little of an oddball being 15×63 instead of a standard 15×70 which is also what makes them very desirable. You get quite a bit more light gathering over a set of 10x50s, with of course 50% more magnification too, but you save a lot of weight making these one of the few larger sets of astronomy binoculars that you can actually hand hold pretty well.
For comparison, these weigh 2.6lbs while the Celestron 15x70s weigh 3.28. That almost three quarters of a pound may not seem like much until you are out in the field holding them up for a hour, then I assure you it is a very big deal.
With excellent optics, good eye relief, very good build quality, and a five year warranty they are every bit worth the money.
For those of you who want the best 15×70 astronomy binoculars out there I suggest the Orion 9546 Resolux 15×70 Waterproof Binoculars. These do not pull punches, they have excellent optics, are fully waterproof, and provide individual eye focusing to make sure you get the absolute sharpest image possible.
Weighing in at 5.5 lbs I am not sure I want to hand hold these monsters for long, thankfully they have a tripod mount screw so I don’t have to. If you want the best astronomy binoculars that can be hand held and give you the best views possible, these are the ones.