If there is a default pair of binoculars for the night sky, it is the 10x50. It has been recommended for decades for a reason that is arithmetic rather than fashion: it is the largest configuration most people can hold steady, at the exit pupil a dark adapted eye can use.
The arithmetic that makes it standard
Fifty millimetres divided by ten times gives a five millimetre exit pupil, which matches the dark adapted pupil of most adults. Ten times is at the edge of what is steady handheld. Together those two facts mean the configuration delivers the maximum useful light to the eye without a tripod, and no other common size does both.
What to look for in a specific pair
Fully multicoated optics, BAK4 prisms, and a real field of view of six degrees or more. Weight matters: a 10x50 between 700 and 900 grams is comfortable for extended viewing, and heavier pairs are usually cheaper glass in a bigger housing.
What it shows on a good night
Every Messier object bright enough for binoculars, which is most of them; the Milky Way resolving into individual stars through Cygnus; Andromeda as a clear elongated glow; the Pleiades filling a third of the field; and comets, which suit the wide field better than any telescope does.
Questions people ask about binoculars
Are 10x50 binoculars good for astronomy?
They are the standard recommendation, because they deliver a five millimetre exit pupil at the limit of handheld steadiness.
What are the best 10x50 binoculars for astronomy?
Any fully multicoated pair with BAK4 prisms and a six degree field from a known maker. Beyond that, the differences are in build and edge sharpness rather than in what you can see.
Should I get 10x50 or 7x50?
Seven by fifty gives a brighter, wider, steadier view with a seven millimetre exit pupil that younger eyes can use fully. Ten by fifty shows more detail. Age matters: pupils shrink over the years, so 7x50 suits younger observers better.