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

Recent content by Binastro

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    Little help with some optics anomalies

    Hi and welcome. It looks like the photo was taken through window glass or some flat glass filter or similar. Regards, B.
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    Engravings German WW1 naval binos

    Distance in metres equals 1/field in radians times total field of view of binocular in metres at the distance of the ship or known object length in metres at right angles to the viewer. The example was at 6.25km or 7,000 yards., where the best accuracy was 70 yards for the rangefinder, but...
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    Can a 25mm binocular resolve sky/cloud detail well?

    Post #13. To me this is just elitism. I spent a decade with a Nipole 7x23 micro reverse prism skeleton binocular in my twenties. It showed me everything I wanted to see. This harping about needing £3,000 binoculars is not how I see things. A good older £100 Porro shows me what I want to see...
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    Aurora Borealis 10 05 24

    Thanks Bri, I saw a similar long lasting display from southern England in the 1980s. There was a large arc in the south probably over or to the south of Paris. As well as maybe a hundred displays from Finland and a few lesser ones from England. However, the best was an all sky halo display in...
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    Nikon EII general question- Zeiss or B&L framed bino?

    Also made in 7x25 and different colours. My 5x25 is rather poorly hand painted and unfortunately opens up more than it should, so I had to mark the correct position. The typical 8x21 folding monoculars open correctly with a proper stop. Regards, B.
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    Can a 25mm binocular resolve sky/cloud detail well?

    There ae numerous micro binoculars of all sizes under many names. I have several 25mm and other sizes. These are reverse prism with prisms outside under the metal. Regards, B.
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    Aurora Borealis 10 05 24

    A beautiful coronal display. Regards, B.
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    Engravings German WW1 naval binos

    Eventually some common sense. A few points though. Although the horizon at 20m height is 16km, this is the sea horizon. If looking at a 20m high bridge of another ship the distance it is seen is double this i.e. 32km. And higher points would be seen also if the air is clear. The accuracy of...
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    Can a 25mm binocular resolve sky/cloud detail well?

    Firstly, clouds don't have detail. Except noctilucent clouds at night at 82km height, and usually 200 miles away unless a very good display when they can be very high, even overhead. June and July. Secondly, looking at sunsets is dangerous, even with a 25mm binocular. However, I did see the...
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    Engravings German WW1 naval binos

    This does, of course, assume that you are viewing at right angles to the ship. If this is not so, a correction has to be made by eye estimation. B.
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    Engravings German WW1 naval binos

    It is very simple. You estimate the number of ships that will fill the field. It can be any number. 5.5 ships is just an example. If the ship's length is known, the full field size can be estimated giving G as a known, but not very exact figure. Then E, the distance is known. B.
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    Engravings German WW1 naval binos

    Rangefinding reticles seem to go back to the 1860s. Micrometer eyepieces maybe earlier. With accurate separations and position angle. B.
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    Engravings German WW1 naval binos

    G is known. If the ship is 150m long 5.5 ships are 825 metres field size. Then E is known. B.
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    Nikon 8x30 EII - Strange Issue Inside Lens?

    Looks like balsam separation. Not fixable at an economic price. Bargains are often not. Regards, B.
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    Engravings German WW1 naval binos

    There are not two unknowns. If one is looking at a ship of known length and if 5.5 ships would fill the field, then the distance is known perhaps to 15% accuracy. I find that reticles are accurate to about 10%. There are Nato reticles, maybe 6,400. Soviet 6,000 Swedish 6,300 but now Nato. It...
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