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#11
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(...)
Thanks for the info. I agree with Jon that the best way to evaluate binoculars is hands on. However this is somewhat problematic with 7x50's as I'd have to do so during the day. Anyway, both my pupils still open to over 7mm so I'm not too worried about wasting much apeture. I'll definitely try to check out the celestrons - I've got a friend who has a pair and I always thought they were excellent. Main reason I like the 7x50's - easy to hold steady (I won't be mounting them) and a wider field of view. Speaking of which, anyone know of any 7x50's with a large field of view? -Eric |
#12
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Tony Flanders wrote:
Paul Lawler wrote in message MOST people's eyes do not open to 7mm even in the darkest locations. I wouldn't go *that* far! It's true that 7x50 binoculars have been downrated since their glory days a couple of decades ago, when they were considered the only binoculars worthy of serious consideration for astronomy. And it's also true that if your pupils only open to 5mm, then 7x50 binoculars won't show any more than 7x35. However, they also won't show any less than 7x35. The only disadvantages of 7x50 as opposed to 7x35 are slightly greater weight and bulk and (possibly) higher price. Set against that is the fact that 7x50 binoculars are more forgiving about interocular spacing and where you place your eyes. If your eyes open to 5mm and your binocular's exit pupils are 5mm, then you have to space the eyepieces *exactly* the right distance and center your eyes *exactly* behind them to take full advantage of the aperture. That's why 7x50 is recommended for use on the deck of a ship. As for 7x50 versus 10x50, the 10x50 will without a doubt show fainter objects, and more detail in all objects. However, the 7x50 have a much wider true field of view (all other things being equal) and are arguably easier to hand-hold. All in all, most astronomers prefer 10x50, 8x40 or some such specifications to 7x50, but 7x50 *certainly* fill an important niche, and will always be the favorite size for some people. - Tony Flanders Why did 7x become associated with 50-mm binoculars? Was the Navy behind it? Did it have something to do with exit pupils, field of view and a moving ship? -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
#13
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Why did 7x become associated with 50-mm binoculars? Was the Navy behind it? Did it have something to do with exit pupils, field of view and a moving ship? I think it had something to do with the cart and chariot wheel spacing that was behind the design of the Roman road system. ;-) |
#14
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Why did 7x become associated with 50-mm binoculars? Was the Navy behind it? Did it have something to do with exit pupils, field of view and a moving ship? Actually, I know that the "bino expert" in our club has explained this to me, as well as why the Japanese came up with a different standard,. However, it probably was in the wee hours of the morning, and I am unable to recall very much. I will get an update in the near future, and will post what I find out. Dennis |
#15
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Thanks for the info. I agree with Jon that the best way to evaluate binoculars is hands on. However this is somewhat problematic with 7x50's as I'd have to do so during the day. Anyway, both my pupils still open to over 7mm so I'm not too worried about wasting much apeture. I'll definitely try to check out the celestrons - I've got a friend who has a pair and I always thought they were excellent. Main reason I like the 7x50's - easy to hold steady (I won't be mounting them) and a wider field of view. Speaking of which, anyone know of any 7x50's with a large field of view? -Eric The Fujinon FMT SX 7x50 has a 7°30' Tfov. They are waterproof, however, they cost $419.95. the quality of the FMY SX Polaris series is known very well. The Fujinon 7x50 WP-XL Marine waterproof has a 7° Tfov and only costs $139.95. I don't know the quality of this binoc. edz |
#17
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#18
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Why did 7x become associated with 50-mm binoculars? Was the Navy behind
it? Did it have something to do with exit pupils, field of view and a moving ship? Many people in their 20s and 30s have a dark-adapted pupil size of approximately 7mm. Thus to take full advantage of one's night vision, a binocular used at night would have an exit pupil of 7mm. Thus a 7x bino would have an objective lens size of 49mm, or 50mm in popular production sizes. Likewise a 10X night bino would be 10x70, and many 11X's are 11x80. In actually practice, for most people, a 7x42 will work just as well. Many people's pupils do not expand all the way to 7mm, especially if you are over 40 (there are exceptions), a lot of night observing is not done under perfectly dark conditions - so if there are some lights around then your eyes might not go to 7mm, and a 7x42 is lighter and easier to hold still. And a decent quality 7x35 is certainly a usable instrument. Likewise for many people a 10x50 may serve them better than a 10x70. While it will be a bit less bright, the weight and size will make using it for extended viewing much easier. There are many other factors to consider for binoculars. Eye relief (if you wear glasses), field of vision (typically binos with very wide fields of vision will not be as sharp), lens coatings, prism quality, etc., etc., . I own a Celestron Ultima 7x42 and it is very nice night and day binocular. Good coatings, relatively light, reasonable field of view, sharp images, good eye relief. Alan |
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