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GlennLeDrew
professor emeritus
Reged: 06/18/08
Posts: 633
Loc: Ottawa, Ontario, Canada
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Re: New 125mm binoculars from Vixen
06/25/08 06:58 PM
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I checked out a pair of Vixens at a star party (Starfest, NW of Toronto) several years ago. They were the fixed power model, working at 30X if I recall. I wasn't impressed. As Edz noted, the exit pupil was undersized, because of a too-small prism aperture which stopped down the system. The collimation wasn't the best, and I didn't see at the time an easy way to tweak this.
The chromatic aberration was just what you'd expect for that size achromat. But the view just wasn't as sharp as it should have been. I attributed it to slight mis-alignments in the prism train, resulting in some astigmatism (no, it wasn't my own eyes--the orientation wasn't right.)
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Some years before, I had built a 5" f/5 right angle bino for a friend, using a pair of decent (~1/3 lambda wavefront error) objectives from American Optical. I used all mirrors (enhanced aluminum) for folding/redirecting the light path. Moreover, I added 2-axis (U/D and L/R) collimation adjustment for one side of the instrument, easily performed by simply turning one or both small knobs. My buddy uses premium eyepieces (mostly Naglers and Panoptics) from 40mm down to 4.8mm. This instrument blows away the Vixen, mainly because I made sure the optical axes entered the eyepieces centered and true. And it can nicely illuminate the huge fields of 2" eyepieces having field stops up to 48mm diameter. For deep sky "fuzzies" they're the shinizzle, and they're not so bad on double stars, either!
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I suspect the newer Vixen will simply be the older model, with new eyepiece barrels replacing the original fixed eyepiece barrel. If that's the case, I don't hold out much hope for an improvement, I'm afraid.
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Home-made 11X50 right angle bino, 8.1 deg. FOV
Modified 26X100 bino, 3.5 deg. FOV
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