Mini-Review Bushnell 4x30 Powerview
Posted 03 December 2008 - 08:37 AM
These are advertised as having 12.5 degree TFOV, pretty impressive. Initially I was shocked when I looked through them and saw a field of view of about 4 degrees.
Eventually, I discovered by moving my head from side to side and peering through the edges of the field I probably could see 10 degrees of width, or more - but not at any one time.
The clue, of course, is the apparent field of view, which calculates out to something under 50 degrees, pretty "straw tube" hole-like, LOL. To say the least, the width of the available field is less than awe inspiring.
The rubber eye tube caps when forced will fold down to some degree, but even then you can't get your eyes close enough to see the wider field, it's just not there unless you shift your view from side to side.
These have no diopter adjustment and don't really offer enough center focus depth to adjust for my bad left eye without my glasses on. With my glasses on they are almost acceptable focus wise, but are just a tad short on eye relief to make this enjoyable.
In terms of night viewing they do add about a single magnitude to my light polluted skies. Field of view is fairly sharp across the center field to it's edges, but that's because you aren't seeing the entire field at any given time. Look all the way horizontally to the real extreme edges and it's quite a mess sharpness wise. Contrast and field brightness are both remarkably poor.
Flimsy focuser easily pushes inwards by accident and has some backlash. Cheap metal frame and limited rubber armor. Not sure if these are really glass lenses and I don't see much in the way of coatings. The objectives are well recessed, which I like.
IPD adjustment is huge. They have to be fully folded to fit in the carry case. Neck strap is nylon string. IPD adjustment greatly impacts TFOV, keep them as wide as you can while in use.
There is no tripod adapter. They are incredibly light. Mechanically and optically these border on being toys or total junk.
I was going to send them back or give them to kid (which I still might do but I hate inflicting junk on kids), but then I discovered them slightly handy for satellite spotting, I'll probably keep them. Good for a laugh if nothing else.
Far from my solution for my gigantic apparent field of view quest, the search continues. I guess you get what you pay for, LOL.
Happy Sky Scanning! - Ted
Posted 03 December 2008 - 01:12 PM
Posted 03 December 2008 - 05:55 PM
They were of fixed-focus design, which I got around by 'breaking' the small glue blob which locked the eyepieces in place. An interesting feature was the ability to laterally translate the eyepiece--kind of like the eccentric adjustments on the objectives of some other binos--to achieve collimation, which of course was set once the eyepieces were glued at the factory.
After some time using them I took them apart, with the intention of making them into a right-angle instrument via the use of Amici prisms. By the way, instead of prisms, the light path was folded by a system of mirrors, which did result in a bit more light loss because of the use of 'standard' reflectance coatings.
I still have the optics, and may one day get around to making a simple RA bino with them...