Choosing the appropriate focal length for my binocular

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Anonymous
2014-01-18
2014-08-24

  • Anonymous
    2014-01-18

    Hi, what focal length should i choose for my binocular (Nikon A211 10x50) in the ocular dialog? I guessed 10 :-( - i'm a beginner. Thanks in advance for any hint. Best regards, Karl

     
  • Kird
    Kird
    2014-01-18

    http://www.nikon.com/news/2013/0129_aculon_a211_01.htm
    This binocular has an objective diameter of 50 mm and it's magnification is 10 times. The focal length is unknown. However, the 'angular field of view' is 6.5°.

    Enter the these numbers in the ocular and telescope dialog:
    eyepiece focal length: 24 mm, aFOV: 68° and field stop: 27 mm.
    telescope focal length: 240 mm, diameter: 50 mm.
    This will show a field of 6.4°.

    If you mark 'Binoculars', then enter 6.5 in the aFOV field and 10 (magnification) in the Focal length field.

     
    Last edit: Kird 2014-01-19
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    • Anonymous
      2014-01-19

      Thank you very much Kird for helping! Your recommended settings look good. Please see the attachments. But how did you get these parameters, especially eyepiece focal length (i thought magnification != focal length ), field stop and telescope focal length? Best regards, Karl

       
  • Kird
    Kird
    2014-01-19

    Focal Length, Apparent Field of View and Field Stop are properties of eyepieces. The values are published by the manufacturer.
    The optics of a telescope have a certain diameter and focal length.
    The magnification of a telescope - eyepiece combination = telescope focal length/eyepiece focal length.
    There is a lot of information on Tele Vue's website: http://www.televue.com/engine/TV3b_page.asp?ID=2
    I used their Eyepiece Calculator (http://www.televue.com/engine/TV3b_page.asp?id=212&plain=TRUE#.UtwabrTb-Uk) to obtain values that correspond more or less to the dimensions of binoculars. (http://en.wikipedia.org/wiki/Binoculars). Mesure the length of the optical path of your Nikon. It will be 200 to 300 mm.
    240 (focal length of objective) divided by 24 (focal length of eyepiece) is 10 (magnification).

    Glad I could help.

     

    • Anonymous
      2014-01-20

      Thank you very much Kird! Best regards, Karl

       
  • Kird
    Kird
    2014-08-02

    Under the 'Eyepieces' tab, mark 'Binoculars'.
    aFOV = 5.9 and Focal length = 8.0 (Field stop = 0.0)

     

  • Anonymous
    2014-08-02

    Thank you very much. You meant "Add" a "Binoculars" and put in the numbers, no ?

     

  • Anonymous
    2014-08-02

    Sorry, you where right. I must "check" "Binoculars".

     


Anonymous


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