What power can be held steady is also an individual phenomena.
If you want good views of the Jovian moons, get a rest
.What determines the best or average in great FOV? We can't focus peripheral vision, yet we can detect movement that surrounds our focus.
I see binos being toted as flat field and sharp to the edge, but narrow FOV and I see others pushing 500' @ 1000 yds that are described as having a nice sweet spot though sharpness falling off well before the edge and enough curvature to require focusing if you wander away from center.
So, I have a 7x36 w/huge FOV lots of pincushion and, although the picture is remarkable and not a lot of fun-house of mirrors effect if you don't pan fast, I have a 8.5x50 that's fairly sharp to the edges, but w/only a narrow 305' FOV.
Granted, both of these were discounted sharing a common price to me of three hundred clams each. I realize the cusp of great glass is beyond my reach, yet what in a 7/8x bino would be considered a reasonable field that's not too narrow?
Regardless of my comparison of 7 vs. 8.5 if I average the twain I have 7.75X43 w/FOV of 385.5'. Doesn't sound bad at all and might be able to cleanly/economically squeeze 400' FOV.
Don't need 43 MM, so 38MM lens. 7.5x38 w/400' FOV in ED glass as an all around bino. Sure, after the release, somewhere down the road the NOS should go for ... Survey Sez! 300 samoleons. Of course if it was a porro that would be the MSRP. So it is written, so shall it be done. Scour the kingdom posthaste for le porro magnifique.
While I'm drifting, what's too much power to hold steady and how far does that apply? I can look inside a hundred yards and the 7x seems steady enough. The moon is about a quarter mill away and I appear to hold a steady frame.
Howevah, when I try to snoop on Jupiter and it's moons, that has a mean distance of 365 mill I think, it's hard to steady the dots. So, at what distance do you determine that you can hand hold a particular power? I have a very basic understanding that multiplication and distance increases movement. Larger targets give the illusion of less movement or maybe small targets are more of a DOH! keep the binos steady Homer type of moment.
One more change of direction to complete the triangle if my short term memory hadn't failed. Why do my diopter settings move from mild minus at close range and end up favoring a tad plus when eyeballin' the night skies?
I know from trips to the DMV every four years that my left eye, besides not being dominate, lags a mite behind the right. At thirty yards and can end up dead center or slightly negative, but when I point to the sky I usually end up easing into the plus column.
What gives? As far as I'm concerned the diopter setting is as a thermostat & I don't care for the numeric value as long as I'm comfortable. That being said there has to be a reason for the subtle changes in shorter/greater lengths or I wouldn't continually notice.
Feel free to ramble, even unto rivers were meant to, if that be your cup of tea.
I don't think there is any sort of standard for what would be considered a reasonable field of view that's not too narrow. That comes down, I think, to individual tastes. The sort of rule of thumb for a wide angle binocular is about 60* AFOV, which in quick terms is the degrees of view multiplied by the magnification. If you can't find the specs for the degrees of fov, just divide the fov by 52.5. Personally I like7-7.5* minimum in an 8x and 6-6.6 n a 10x. Some don't mind less, some want more. There is a lot of individual preference in edge of field performance, or any other parameter. Some things are only answered by the individual. Comes down to what you like.
What power can be held steady is also an individual phenomena.
If you want good views of the Jovian moons, get a rest .
First, resist the urge to observe solar system objects with binoculars. That's why they make telescopes.
Second, instead of spending $300 a pop for several lesser quality astro binoculars, spend ~$600 for a Fujinon FMT10x50, Nikon SE12x50 for mounted use, or the Canon 15x50IS for handheld. If you predominately prefer astro binocular observing over a telescope, then you really want to get a 15x70mm, 20x80, or 25x100 size.
Finally, your need to change the diopter position from close to far suggest improper focusing technique or more likely, binoculars with collimation or other QC issues.