Some things to look out for when buying a pair of astronomical binoculars are its aperture and exit pupil. Astronomical binoculars should have an aperture of at least 40mm to gather sufficient light for night observation. For astronomy purposes, it is best to go for binoculars that magnify at least 7 times. Binoculars exceeding 10x in magnification and 50mm in aperture will need a tripod to deliver good, steady views of the night sky.
Another key feature is the exit pupil, which is the width of the beam of light as it leaves the eyepiece. This is calculated by dividing the aperture by the magnification, so for example a 10x50 binoculars would have an exit pupil of 5mm. Our maximum pupil size decreases with age – below 30 we have a maximum pupil size of 7mm, and this decreases to 5mm when you reach 40. Choose binoculars with the same exit pupil as your eye's pupil, as binoculars with a wider exit pupil than your own will cause some of the images to appear dimmer as some of the incoming light won't get into your eyes.
Astronomical binoculars have a wider field-of-view, which makes it easier to spot faint objects such as outer planets like Uranus and Neptune. They work best when viewing large deep sky objects such as the Milky Way star fields, big star clusters, and large nebulae. If you're unsure of which astronomical binoculars to choose, feel free to contact us and we'll be happy to answer any questions you may have.