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ZEISS DTI thermal imaging cameras. For more discoveries at night, and during the day.

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  1. B

    New way to determine the weight of binoculars?

    I measure fields of view from accurate star separations. A good one is alpha to beta Ursa Major at 5 degrees 22.4 minutes from memory. There are numerous others, but one tries to get as close to the limit as possible. There are internet programmes, which are accurate. For spotting scopes the...
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    New way to determine the weight of binoculars?

    The large Leica optics catalogue gives full specifications of all items. The 12x50 Ultravid is stated to be approx. 1040g. I weighed it and it is 1046g calibrated. So it is slightly more than stated, but I think acceptable. I suppose they could have said approx. 1050g, but as mentioned...
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    Is my Spotting Scope decent enough?

    The detail shown on the Moon is good. However, the Moon is an easy large object. I probably get similar detail with Nikon, Minolta, Canon, Tamron SP and Optomax 500mm f/8 mirror lenses with 2x or 3x teleconverters. The MTO 1000mm f/10 isn't usually as good, but The Vivitar 600mm f/8 solid Cat...
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    New way to determine the weight of binoculars?

    The image in post #1 shows 659g and 668g in post #20. I assume this is the same binocular and that the amount of strap added in post #20 is 9g. If Swarovski are quoting weights without eyecups this may be dishonest. Or it may be the armour has changed or internal changes made over time...
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    New way to determine the weight of binoculars?

    A change in the thickness and density of rubber armour could account for some or all of the 19g difference. Has the rubber armour changed over time? Regards, B.
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    New way to determine the weight of binoculars?

    With the 1Kg accurate calibration weight, the scales indicate 1007g, which is what they have always done. I took this 1Kg weight to the post office and from memory the 5 post office scales varied by one or two grams. I corrected binocular weights indicated by 0.7%. Sometimes the weight of a...
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    Viking Binos - prism alignment build quality.

    Most binoculars can be knocked out of alignment rather easily, although some expensive brands can take quite hard knocks without a problem. Usually this is not covered by warranty. Military binoculars are usually better. Camera lenses can also get knocked out, but often a dented filter thread...
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    New way to determine the weight of binoculars?

    I use a digital scale, but have calibrated accurate weights. I mainly use 500g, 1kg and sometimes 2kg expensive weights that I keep clean and covered for calibration. I also have smaller weights. I take perhaps three readings. The weight can differ depending on where and how the binocular is...
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    Is curvature of field a good thing?

    It may be that the Cooke Speed Panchro f/2 was used. The 50mm f/2 is I think a 7 element 5 group lens of double Gauss type. These lenses, in many different focal lengths, were designed by Horace Lee in 1920 and were used in most movies for perhaps fifty years. There are new production...
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    Kowa 99 Update?

    There may have been only one master optical worker at Kowa. He may have retired. There may be one at Swarovski, one at Leica, one at Canon, one at Nikon and two at Zeiss. There are some in France, U.K., U.S.A., Netherlands, Belgium, Australia, probably Russia and elsewhere. But when they...
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    Best low- to mid-priced monocular

    Opticron have various monoculars. Regards, B.
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    Is curvature of field a good thing?

    Space is essentially curved, but so distant that it seems flat. Photo lenses definitely try to achieve flat fields. Even a well made Cooke triplet has an almost flat field. Projecting slides from Gauss type 5, 6 or 7 element lenses the whole field, say 4ft or 5ft wide can be flat...
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    A Cure for Swinging Binoculars

    I think the 6400 must refer to the reticle so called milrad, which is the later Nato standard. Sweden used 6300, later 6400. Soviet 6,000. It should be 6283 (2Pi x1000). I don't think reticles are interchangeable. Regards, B.
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    Wide flat field and edge sharpness an illusion?

    The best test of edge sharpness is to use a fixed mirror mount and let the stars drift over the field. You then see how awful edge performance is in many binoculars that are perfectly O.K. in normal use. Regards, B.
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    Determining the date of manufacture of the Hartmann Wetzlar binoculars

    Hi and welcome. The binocular looks genuine, but I don't know when made. The binocular seems to be in good condition, hopefully well aligned and free from internal moisture or fungus. Regards, B.
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    10x42L vs Nikon MHG

    Firstly, the Fujinons, at least the older 14x40s have an annoying jiggling that makes them unusable for me and others. The image is clean and good but the jiggling unacceptable to me. I did estimate the amplitude and frequency but cannot remember what they are. Yes, indeed, tripod mounted IS...
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    Challenge - shortest, clearest explanation of why 8x FOV tends to be greater than 7x and 10x

    7x50s are usually either marine binoculars or simple binoculars with fields typically of 7.1 degrees. There are wide field 7x35s, such as the Minolta Standard MK with 11.05 degrees measured field and some up to about 12.5 degrees, but the 7x50s usually have smaller fields. The Minolta Standard...
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    Engravings German WW1 naval binos

    As with all binocular fields measured in angles of degrees or radians, these are spherical or circular measures. Expressing fields of view in linear terms, say metres, is imagining a flat plane or linear measure. As the binocular field gets wider there is more of a difference. However, here...
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    Engravings German WW1 naval binos

    See post 18. This is an O level Mathematics question for 16 year olds. E is the distance in metres. N is 1 divided by the field of view in radians with a possible empirical correction for distortion. In other words, How many field widths of the binocular fill one radian or 57.3 degrees? In...
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    Stopping down a binocular

    The 8x32BA weigh 640.5g. The 8x32 Conquest HD 628.5g. So 12g or less than 0.5oz difference. Or 2%. I had to change the scales battery and didn't have time to calibrate the scales, but probably correct. Regards, B.
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    New binos by mid June.

    But, as I said before, you have to buy the binocular you actually test and not some remote binocular, as there is considerable sample variation. Ask B and H if they will give a discount on either the demonstrator or a new one that you actually test. In my opinion it is false economy to test in...
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    Stopping down a binocular

    Any good optic can lose sharpness if an element is tilted or moved sideways. Today I tested the 8x32 BA against a Zeiss Conquest 8x32 HD. Both were equally sharp, with the Conquest brighter, but personally I don't like the very quick focus as at my normal 120m distance. It was difficult to...
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    Upgrade to TSN-88 from TSN-883?

    Uusi tai vanha? If you buy a new Kowa, make sure it is a cherry example, as even the top scopes seem to have sample variation, with some being poor optically. So maybe test any new possible purchase directly against your current scope. Regards, B.
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    Upgrade to TSN-88 from TSN-883?

    It is a personal thing. If there are any defects in your present scope, maybe change. New is not always better. Terveisin. B.