Choosing Binoculars for Astronomy
Binoculars are an inexpensive, perhaps essential, way to get started in astronomy. Many people consider binoculars to be a necessity and will recommend learning the constellations and how to find night-sky objects first using binoculars before going out and buying a telescope. Even when using a telescope, your star-gazing will be enhanced by the ease of use and wide field of view of having a good pair of binoculars with you.
Astronomy is kind of a special application for binoculars. Binoculars sold at sports stores or department stores aren't suited for night-sky viewing - their optics just aren't up to par. Plan to spend an absolute minimum of $75 for a decent pair of binoculars for astronomy from a reputable camera or telescope store. Also see Types of Binoculars.
The best all-around binoculars for astronomy are either 7x50 or 10x50. 7x50 binoculars will give you an exit pupil of 7mm, which is the largest you want to use. 10x50 binoculars have a 5mm exit pupil, which is even better. If you are over 40 years old, your maximum dilated pupil size at night will probably be closer to 5mm. The smaller the exit pupil, the brighter the image will be, but the closer your eye must also be to the eyepiece, which can make them harder for some people to use.
Do's for Buying Binoculars
- Consider a 7x50 or 10x50 model - this will allow steady hand-holding without binocular shake
- Spend at least $75 for acceptable-quality binoculars
- Get a model that will mount on a camera tripod - look for a threaded hole in the front
- Get a tripod, this is a low-cost way to stabilize your binoculars
- Consider getting a pair of solar filters for viewing sunspots and other solar activity
- Porro-prism type binoculars are generally better than roof-prism binoculars.
Dont's for Buying Binoculars
- Don't buy from a department or sports store - these are not suited for astronomy
- Don't buy a fixed-focus or "perm-focus" model - these are not suited for astronomy
- Don't buy zoom binoculars - optical quality is compromised to keep costs down
- Stay away from the compact, roof-prism type of binoculars