Bushnell PowerView 20×50 Binoculars: High Power Explained for Beginners

The original post on this site was a sales description of the Bushnell PowerView 20×50 “super high-powered” binocular. This rewrite uses specifications from the B&H Photo listing for the PowerView 20×50 (model 132050) and explains what such high magnification means in practice.

Verified specifications

From B&H Photo’s listing for the Bushnell PowerView 20×50 (132050):

• Magnification: 20x; objective diameter: 50 mm
• BK7 Porro prisms
• Fully multi-coated optics
• Actual angle of view: 3.2°; apparent angle of view: 65°
• Field of view: 168.7 ft / 56 m at 1,000 m
• Exit pupil: 2.5 mm
• Eye relief: 9 mm
• Minimum focus distance: 44.9 ft (13.7 m)
• Centre focus with InstaFocus rocking lever; right-eye diopter
• Fold-down rubber eyecups
• Tripod mountable with an optional adapter
• Weight: 30 oz (851 g)
• Included: case, caps, strap and cleaning cloth

Corrections to the original listing

• B&H’s description says “170-foot field of view at 1000 yards” while its specification table says 168.7 ft at 1,000 m. A 3.2° field equals about 168 ft at 1,000 yards, so the table’s “per 1,000 m” label looks like a unit mix-up.

What the numbers mean

Every binocular carries two numbers. Astronomy magazine’s binocular guide explains that the first is the magnification and the second is the diameter of each front lens in millimetres, so a 20×50 magnifies 20 times and has 50 mm lenses.

• Exit pupil: aperture divided by magnification. 50 ÷ 20 gives 2.5 mm, small for night use; Nikon’s guide notes that a small exit pupil makes the image darker.
• Why exit pupil matters at night: the same guide says most people under 30 have dark-adapted pupils of about 7 mm, around 6 mm in their 30s, and probably no more than 5 mm from age 40. A bigger exit pupil than your eye can use simply wastes light.
• Field of view: to convert feet at 1,000 yards into degrees, divide by 52.5. 3.2° is very narrow, which makes finding things harder. Astronomy magazine says most binoculars cover about 6° to 7°, high-power models 3° to 5°, and wide-angle models 8° to 10°.
• Eye relief: Nikon’s guide says eye relief of 15 mm or longer lets most eyeglass wearers see the whole field without removing their glasses. At 9 mm, this binocular is not well suited to glasses.

Is it good for stargazing?

Astronomy magazine says about 10x is the most you will want hand-held and that giant binoculars, above 10x with large apertures, need a tripod. Nikon’s guide adds that high magnification brings a narrow field, unstable images from hand movement, and a small, dark exit pupil. At 20x all three apply, so treat the PowerView 20×50 as a tripod instrument. On a tripod it can give a closer look at the Moon and Jupiter’s big moons, but the 2.5 mm exit pupil makes it less suited to faint deep-sky objects than a 10×50.

Setting up your binoculars

Bushnell’s Trophy owner’s guide describes the standard set-up that works for most centre-focus binoculars:

• Eyecups: twist them up if you do not wear glasses, so your eyes sit at the right eye relief distance and you see the full field of view.
• Interpupillary distance: point the binoculars at a blank wall or sky and move the two halves closer or farther apart until you see a single circle with no shaded areas.
• Focus the left side: cover the right objective lens, then turn the centre focus knob until a detailed distant object looks sharp through the left side.
• Set the diopter: cover the left lens instead and turn the diopter ring under the right eyepiece, not the centre knob, until the right side is sharp.
• Remember your setting: note the diopter mark so you can reset it if someone else uses your binoculars.

What you can see in the night sky

According to Astronomy magazine, binoculars show the Moon in crisp detail, including shadows moving across lunar features as it waxes and wanes and earthshine on a crescent Moon. They also let you follow the phases of Venus and the motions of Jupiter’s big moons. Beyond the solar system, large star clusters such as the Pleiades in Taurus and the Beehive in Cancer fit nicely in a binocular view, and the Andromeda Galaxy (M31) stands out from a dark site. The magazine says more than 400 deep-sky objects lie within reach of good binoculars from a dark-sky site.

Care and cleaning

The Trophy guide’s cleaning advice applies to any binocular: blow or brush away dust first, then wipe in a circular motion with a microfibre cloth. For a thorough clean, use photographic lens tissue and lens-cleaning fluid, always applied to the cloth and never directly on the lens. Never use household window cleaner or paper towels, which can damage coatings or scratch the glass. Store the binoculars in a cool, dry place.

Safety

Never look at the Sun through binoculars or any optical instrument. Bushnell’s guide warns this may permanently damage your eyes.

Quick summary

• 20×50 BK7 Porro prism, fully multi-coated.
• 3.2° field; 2.5 mm exit pupil; 9 mm eye relief.
• InstaFocus lever; 30 oz.
• Use a tripod; best for the Moon and bright targets.

Jargon buster

• Objective lens: the big front lens that collects light.
• Exit pupil: the small bright circle of light you see in each eyepiece when you hold the binoculars away from your eyes.
• Diopter: an adjustment for differences between your two eyes.
• Roof vs Porro prism: roof models have straight barrels; Porro models have the classic zigzag shape.