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  1. #1
    John Carruthers's Avatar
    John Carruthers Guest

    Default Orthoscopic FOV ?




    Just bought a no name 6mm orthoscopic on e-bay, what might the
    apparent FOV be typically ?
    jc
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    http://mysite.wanadoo-members.co.uk/jc_atm/



  2. #2
    CLT's Avatar
    CLT Guest

    Default Orthoscopic FOV ?

    Hi John,

    If it is a true Abbe design ortho, it should be close to 45 degrees.

    Clear Skies

    Chuck Taylor
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    Try http://groups.yahoo.com/group/lunar-observing/

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    "John Carruthers" <joncarruthersnotthisbit@hotmail.com> wrote in message
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  3. #3
    Ed T's Avatar
    Ed T Guest

    Default Orthoscopic FOV ?


    "John Carruthers" <joncarruthersnotthisbit@hotmail.com> wrote in message


    Generally 40-45 degrees. Eye relief is 80% of focal length, roughly. Thats
    assuming its a traditional 4 element orthoscopic. There are a number of
    oculars labeled orthoscopic that have 3-5 elements.

    Ed T.



  4. #4
    John Carruthers's Avatar
    John Carruthers Guest

    Default Orthoscopic FOV ?

    Thanks guys, that's all I need.
    jc

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    http://mysite.wanadoo-members.co.uk/jc_atm/



  5. #5
    Phil Hawkins's Avatar
    Phil Hawkins Guest

    Default Orthoscopic FOV ?

    Ed T wrote:
    Ed (or others)
    At the risk of seeming dumb, (Although a post to another thread earlier
    today might have already set that in concrete !!!), can you explain how
    to get the app FOV?
    My cheap scope has two eyepieces with no FOV marked. They are 10mm and
    20mm. The scope is 130/900 mm
    Appreciate the assistance
    Regards
    Phil

  6. #6
    RichA's Avatar
    RichA Guest

    Default Orthoscopic FOV ?

    On Fri, 11 Mar 2005 18:23:06 GMT, "Ed T" <reply@thegroup.thx> wrote:


    Celestron labelled some Plossls as orthos in the 1980s.
    -Rich

  7. #7
    Ed T's Avatar
    Ed T Guest

    Default Orthoscopic FOV ?


    "Phil Hawkins" wrote in message


    Phil,

    The most accurate way to determine the apparent fov is to measure the actual
    FOV and multiplying by the magnification. For example, if your view is 2
    degrees (per a star chart or the drift method) and your magnification is
    25x, then the apparent field of view is 50 degrees. There are some methods
    here:

    http://steve_bell.home.att.net/astromath.html

    The easiest way to determine the apparent FOV is to read the manufacturers
    specifications ;^) They never (seldom, anyway) mark them on the eyepiece
    but they're often available on the web. If the type and make is not known,
    you're back to measuring or estimating.

    Ed T.



  8. #8
    Brian Tung's Avatar
    Brian Tung Guest

    Default Orthoscopic FOV ?

    Ed T wrote:

    Although this method works with orthoscopic eyepieces, it may yield
    somewhat inaccurate results if used with eyepieces with significant
    levels of distortion (usually pincushion distortion). There are ways
    to measure the AFOV directly. See MOPFAQ (link below) for one way.

    Brian Tung <brian@isi.edu>
    The Astronomy Corner at http://astro.isi.edu/
    Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
    The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/
    My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.txt

  9. #9
    John Carruthers's Avatar
    John Carruthers Guest

    Default Orthoscopic FOV ?

    >Celestron labelled some Plossls as orthos in the 1980s.<

    Great, I'll let you know when it gets here.
    jc


    --
    http://mysite.wanadoo-members.co.uk/jc_atm/



  10. #10
    Lawrence Sayre's Avatar
    Lawrence Sayre Guest

    Default Orthoscopic FOV ?

    RichA wrote:

    Plossl's are fully orthoscopic, are they not (as are several other types
    of eyepieces)? Perhaps this is just a big 'O' little 'o' thing. :-)

    Lawrence Sayre

    --
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    as the same is now current, and to contain three hundred and seventy-one
    grains and four sixteenth parts of a grain of pure, or four hundred and
    sixteen grains of standard silver.". Don't be fooled by valueless paper
    "notes" (debt instruments) masquerading as "Dollars". A Dollar is and
    always has been only "silver", and more specifically 371.25 grains of
    ..999 pure silver.

 

 
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