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  1. T

    Wide flat field and edge sharpness an illusion?

    These attributes combined with adequate eye relief for glasses wearers are an outstanding (and recent) optical achievement, but for hand-held binoculars they are of no practical value. The fovea of the human eye, where highest visual acuity for 20/20 vision is achieved only has a visual field of...
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    Vignetting in Binoculars

    This is a topic rarely discussed on Birdforum, but one that has an influence on the performance and perhaps subjective appreciation of binoculars. Vignetting is a loss of brightness towards the field edge and is present in all binoculars. It is caused by obstructions, usually baffles, in the...
  3. T

    First Love Rekindled

    About twenty years ago I bought my first "good" binocular, a 7x42 SLC. A few weeks earlier the Photokina exhibition in my home city had offered the opportunity of testing most of what was available. I was less experienced then although my eyesight was better and presbiopia had not advanced...
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    Biathlon

    is a popular spectator sport in many European countries and in TV broadcasts one sometimes catches a glimpse of the spotting scopes used by the coaches. They mark a board showing the impacts so that the athletes can make necessary adjustments to their sights at the next shooting. In today's...
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    Dielectric Coatings - Potential Drawbacks?

    Schmidt-Pechan prisms are the most widely used roof prism type in current binoculars. Compared to Abbe-König prisms they are more compact but have two disadvantages. The first, which has been widely discussed here, is the need for one prism surface to provide total internal reflection and direct...
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    Product Placement or Advertising?

    Yesterday evening I watched a programme on 3sat, "Die Magie der Vögel", the magic of birds. Now 3sat is a cooperative of public TV companies in Germany, Switzerland and Austria and is theoretically free of advertising. This Austrian-produced programme showed various aspects of birdwatching but...
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    Parfocality Limitations

    A zoom objective lens or eyepiece is considered parfocal if its focal plane remains constant at all focal lengths, allowing a change of magnification without altering focus. Some sets of astronomical eyepieces of different focal lengths are also claimed to be parfocal. In a review of the 85 mm...
  8. T

    A trivial thought.....

    .....on the vesatility of birding optics. Another member recently posted observations of insects and I once directed my scope at a wood ants' nest at close range. I have also observed the Andromeda Galaxy through a binocular. Now, wood ants are about 1 cm long and the Andromeda Galaxy has a...
  9. T

    "Better Glass"

    How many times have we read that on Birdforum? However, none of us consumers has much idea what glass is used in our optics and what is "better glass" anyway? Some manufacturers of astronomical telescopes advertise low dispersion glass such as FPL-53 used in their objectives, Kowa use Calcium...
  10. T

    Eyeglasses - a few unqualified remarks

    We haven't seen much of our resident optician Looksharp65 recently, so here are a few observations open to correction. Use with binoculars:- If one cannot see clearly at moderate distances with the naked eyes, due either to near-sightedness, advanced presbyopia or astigmatism, then one is going...
  11. T

    Birding Scope plus Barlow.

    A barlow is a negative lens placed between the telescope objective and the eyepiece and effectively increases the focal length of the objective to provide a magnification increase, usually around 2x. It is often asserted that a barlow will increase the eye relief, but this is not true. For the...
  12. T

    Do higher scope magnifications make any sense?

    By "higher" I mean magnifications with a numerical value greater than half the objective diameter in millimetres. This concept is such a radical departure from accepted thought that I have my own doubts and would appreciate some qualified comments. I was out birding with a friend yesterday and...
  13. T

    Resolution measurement 8x56 SLC

    I have tried several times in the past to measure the resolution of my binoculars using an Edmund Optics USAF 1951 glass slide and a 3x12 Zeiss tripler but failed, firstly because of the diificulty in affixing the tripler behind the binoculars' ocular and secondly because my old eyes require...
  14. T

    Don't use thread adapters!

    Many scope users seem to favour direct mounting of the scope into the tripod head. Some scope feet were compatible with the Manfrotto RC system and now later Swarovski scopes are Arca-Swiss compatible. Perhaps there was a fear that quick-release plates could come loose, but for many scopes a...
  15. T

    Partial Solar Eclipse Today

    I was able to view the partial solar eclipse today. Here in Cologne it lasted from 11.10 to 13.06 Central European Summer Time with a maximum coverage of 22%. I used my ATM65 HD with 30x eyepiece and a filter I had cobbled up with Baader Astro Solar fim. It's quite a challege trying to find the...
  16. T

    Crash Course Astronomy

    I've just discovered these videos although they are a few years old. Absolutely fascinating stuff and something there from which everyone could learn. There are over 30 of them and #6 is about telescopes. John
  17. T

    AFoV Calculations

    There are two methods of calculating the apparent field of view. The first is to multiply the true FoV in degrees by the magnification of the binocular. The second ISO method is to calculate the angle as if the binocular were nearer by a factor of its magnification. To take an example, the...
  18. T

    Juggling with Magnifications

    Puzzlingly large differences in weight and overall length of two related 42 mm binoculars provoked this thread, but more on that later. Magnification is the ratio of objective focal length to eyepiece focal length or alternatively, objective aperture to exit pupil diameter. If a manufacturer...
  19. T

    Focussing: Just Do It!

    This post, is not about technique. On the contrary, it is intended to dispel the concept that one should adopt a special technique to relax the eye muscles, or that one should focus from near to far, which could be problematical in some field situations! Following on from my thread on "Dioptre...
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    Berlebach Report Wooden Tripod

    I think most of us would be well served by a decent 8x42 and if our interests (waders, ducks etc.) demanded it, by the addition of a medium-sized scope and tripod. However, nearly all of us are afflicted with NAJS (new acquisition justification syndrome), typically: "I need a new binocular for...
  21. T

    Berlebach Service

    I have owned a Berlebach 552 for about 10 years and still consider it, together with its successor the 553 to be the ideal 2-way head for use with a birding scope. A few weeks back the panorama function started feeling a bit gritty, probably due to ingress of some debris, so I applied a drop of...
  22. T

    When the Wind Blows

    At the beginning of April I took a 10 day trip to the German North Sea coast near Meldorf. It's an excellent site and at high tide most of the birds fly in from the mud flats to the salt marshes to rest. Unfortunately, after a mild spell at the end of March the weather turned cold again with...
  23. T

    A Comparison of "3-Series" Systematic Tripods

    https://www.dpreview.com/reviews/tested-six-large-tripods-for-heavy-duty-use#testing An interesting comparison even if these tripods offer more than some scope users would need and cost more than many would be prepared to pay. Here is a ranking of systematic tripods: Systematic Tripod Rankings...
  24. T

    Dioptre Setting: Fallacy and Fact

    There are frequent misunderstandings and misconceptions on dioptre setting and many are of the opinion that the dioptre should be set on an object at or near infinity. Conversely, would they expect the dioptre setting to be wrong for objects at shorter distances? On another thread I asserted...
  25. T

    Zeiss 3x12 Monocular

    I have owned this instrument for several years but an observation today prompted me to post. The variously designated 3x12B or 3x12T* (mine) has been in production for at least 30 years and AFAIK the only significant change has been phase coating and current manufacture in Hungary. Of the six...
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