Telescope Reviews: Are 7x50's any good at anything?

Joe,

I think what you might be referring to as a "seeing measurement for binos" is "hand held resolution".

For an explanation of how various configurations resolved detail both hand held and mounted see Edz's report (note: a 7x50 was not included in this study):

Binocular Resolution Handheld versus Mounted

As far as what 7x50s are good for depends on what you use them for during the daytime, and for stargazing, the size of your entrance pupil, sky darkness, and what you want to observe.

For daytime use, a 7x42 or 7x35 would work just as well, perhaps even better for users with smaller hands, because sunlight is going to shrink your entrance pupils too small to take advantage of the 7mm exit pupil of a 7x50. So why carry the extra weight and bulk? Or at least bulk, the Vista 7x50 is lightweight compared to most IF EP 7x50s.

If you use the 7x50s for boating (one of the chief uses for this configuration -- "marine binoculars"), the larger exit pupils will give you more "wriggle room" to avoid blackouts if your eyes wander off center as the boat rides through the water.

If you are a landlubber with shaky hands, the 7x could also help, though again, the magnification is more important than the objective size for daytime use.

For stargazing, the usefulness of a 7x50 depends on several factors. One of them is the relative darkness of your skies.
My skies are light polluted so even though my dark adapted pupils do not open to 7mm, the skies are washed out with a 7x50 or 8x50 binocular. With faint fuzzies, contrast is important, so I can actually see better detail with smaller exit pupil bins even though their objective size is less.

I'm not sure why this is. I'll let Edz or someone else chime in with an explanation if they agree.

In theory, light polluted skies should "stop down" my entrance pupils to about 4mm, so a 7x50 and a 7x35 should work the same (7x28), because my maximum entrance pupils under bright skies are around 4mm.

But in actual use, the 7x35 bin gives me better contrast whereas the sky looks washed out in the 7x50.

Even if I can max out my entrance pupils to 5mm, the 7x50 would operate at the same configuration for my eyes as the 7x35.

In any case, I find a 7x50 gives me significantly less contrast under my suburban skies so this makes them less desirable than a 7x35, and since I use bins for both stargazing and birdwatching, I also prefer the closer focus and wider FOV of a 7x35 binocular.

I find that 7x doesn't show me enough detail for stargazing except for sweeping the Milky Way and looking at open clusters, and for that kind of observing, I prefer the wider FOV, larger apparent FOV, and higher magnification that my 8.5x44 Swift Audubon provides.

So for me, at least, the extra steadiness and larger objective that a 7x50 offers for stargazing is outweighed by the greater detail, wider field of view, and better contrast I get from a good quality 8x42 binocular, or even my 8x32 SE.

In fact, during one my club's public outreach events, I compared a fellow club member's Fuji 7x50 to my Vista 8x42. I preferred the views though the Vista for stargazing under our light polluted skies even though the Fuji is legendary for stargazing and the Vista's FOV was slightly narrower (6.5*). So did he, and he promptly sold his Fujis and bought my Vistas.

YMMV.

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Oscar Zoroaster Diggs
"O.Z."

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