Best Binoculars for Astronomy

For the night sky, the number to watch is the exit pupil: objective diameter divided by magnification. The larger it is, the brighter the view stays in the dark. Astronomy binoculars fall into three groups by how they are held, and that matters more than price.

The handheld group is the 10x50. The Pentax SP 10x50 WP ($199) is a porro that focuses internally, which lets it be fully sealed. Owners report pinpoint stars, little ghosting on the moon and 20mm of eye relief. The trade-offs are a narrow 262 ft field and 37.4 oz of weight. The Nikon Monarch M5 10x50 ($390) brings ED glass and 19.3mm of eye relief in a 22.6 oz roof-prism body, so it carries easily between sky and daytime use. Both give a 5mm exit pupil, bright enough for the Milky Way and open clusters, with a field wide enough to find them.

The tripod group starts with the 70mm porros. The Celestron SkyMaster 15x70 at $130 is the cheapest large-aperture view in this group, with a 4.7mm exit pupil at 48 oz. Owners love it for its price and are blunt about its faults. Pairs often arrive out of collimation, the effective aperture is smaller than 70mm, and about 30 seconds of handholding is the limit. The SkyMaster Pro 15x70 ($280) is the better-built version of the same format. The SkyMaster 25x70 ($140) is the one owners most often advise against for stargazing: its 2.8mm exit pupil and 141 ft field make the sky dim and hard to search, though on a solid mount it shows lunar craters well. The Maven B.5 18x56 ($1,850), built for hunters glassing from a tripod, adds fluorite glass and 18mm of eye relief, but its 3.1mm exit pupil still limits faint objects.

The third group trades the tripod for electronics. The Canon 18x50 IS AW ($1,549) stabilizes 18x by hand, and owners describe globular clusters and the Ring Nebula seen without a mount. It weighs 41.6 oz, its stabilizer is slow to settle, and its eye relief behaves nearer 10mm in use. The Steiner HX 15x56 ($1,000) is out of production.