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  1. #1
    Tony Flanders's Avatar
    Tony Flanders Guest

    Default AFOV vs Aperture Poll



    Here are the results of a "poll" that I initiated in the
    middle of a thread with the dopey title "What's so Great
    about Tele Vue Eyepieces?" I was hoping to get some sense
    of the value that people place on a wide AFOV by presenting
    the following choice:

    Suppose you had to spend the rest of your life on a desert
    island with one of the following sets of equipment, which
    would you choose?

    * An 8-inch scope with a full set of 80-degree-AFOV EPs.
    * A 10-inch scope with a full set of 50-degree-AFOV EPs.

    I mentioned Plossls and Naglers specifically, but my real
    intention was to assume that all other things are equal
    except the apertures of the scopes and the AFOV of the EPs.

    Needless to say, this is not a realistic scenario.
    Nonetheless, the results are quite instructive; people
    fall into four camps:

    * One person (Jon Isaacs) refuses to take the bait;
    apples are apples, oranges are oranges, and he'll
    deal with the desert island when and if he has to.

    * Three people (Howard Lester, David Knisely, and me)
    after hemming, hawing, and qualifying, come down quite
    clearly on the side of aperture. From our point of
    view, AFOV is definitely a second-order issue, to
    be considered only after first-order issues like
    aperture.

    * Two people (Bill Meyers and Stephen Paul) come down
    quite clearly on the side of AFOV, citing in particular
    the esthetic benefits of a wide AFOV.

    * Two people (Axel and Bill Ferris) lean towards aperture
    but qualify this depending on the details of the
    circumstances, citing primarily the practical
    (rather than esthetic) benefits of a wide AFOV.

    I am not sure that I like my use of the term "esthetic"
    above; after all, one could argue that *all* visual
    observing is fundamentally driven by esthetics. Visual
    observing is not completely dead as a means of obtaining
    practical data, but it is at a pretty severe disadvantage
    compared to electronic imaging.

    It is also interesting that despite the relatively low value
    that I place on the esthetics of AFOV, I place a very high
    value on the esthetics of dark skies, as evidenced by my
    other thought experiment, where I choose lifelong exile
    under dark skies with 10x50 binoculars to a life under
    perpetual full Moon with a 12-inch scope. This is clearly
    a matter of esthetic preference, because by any reasonable
    measure, one can see *far* more with a 12-inch scope under
    full Moon than with 10x50 binoculars under a dark sky.

    - Tony Flanders

  2. #2
    Brian Tung's Avatar
    Brian Tung Guest

    Default AFOV vs Aperture Poll

    Tony Flanders wrote:

    Four, actually. I'm not sure why Google is refusing to archive my posts
    on this thread, since I don't put that particular header in my posts.

    BTW, I don't hem and haw--not on this issue, since I've given it some
    thought in the past in response to similar questions.

    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

  3. #3
    Michael A. Covington's Avatar
    Michael A. Covington Guest

    Default AFOV vs Aperture Poll

    In my youth (the early 1970s), 50 degrees *was* wide field. For a while
    there, my best eyepiece was a Ramsden with a 30-degree field.

    I would choose an 8-inch with 20-mm-eye-relief eyepieces over a 10-inch with
    conventional eyepieces.

    And my preferred AFOV is about 60 to 65 degrees. Radians and Pentax XLs for
    me!



  4. #4
    Bill Ferris's Avatar
    Bill Ferris Guest

    Default AFOV vs Aperture Poll

    Tony Flanders wrote:

    Where lunar/planetary observing is concerned, the 12-inch under would obviously
    outperform a pair of 10x50 binocs, regardless of light pollution. But for
    deep-sky observing, dark and transparent skies are the key.

    Given the choice between the binocs under pristine skies and a 12-inch under
    heavily light-polluted skies, I'd take the binocs under dark skies without
    hesitation. And it wouldn't be a choice based on aesthetics. It would be based
    on the superior performance of the smaller aperture under truly dark skies.

    Regards,

    Bill Ferris
    "Cosmic Voyage: The Online Resource for Amateur Astronomers"
    URL: http://www.cosmic-voyage.net
    =============
    Email: Remove "ic" from .comic above to respond


  5. #5
    Michael A. Covington's Avatar
    Michael A. Covington Guest

    Default AFOV vs Aperture Poll

    "Bill Ferris" <billferris@aol.comic> wrote in message
    news:20031228220933.19067.00001722@mb-m13.aol.com...
    obviously
    under
    based
    skies.

    Amen! A few years ago, the tour guide at Kitt Peak was a little puzzled
    that instead of lining up inside the 16-inch dome, I was outside reclining
    on a boulder, using my 8x40 binoculars. But then I told him what I was
    observing... galaxies down to 9th mag. or more... and so forth...

    I can use a telescope back home. I can't see what I was seeing in those
    binoculars!

    (And boulders are handy too. We need one for the yard...)




  6. #6
    starburst's Avatar
    starburst Guest

    Default AFOV vs Aperture Poll

    Make it five. Desert Island... no light polution... dark skies... mmmm. I'll
    take the aperture any day of the week and twice on Sunday. I remember when
    my kellner with a 40 degree field was a big step up. I can live with 50
    degree fields and deeper limiting magnitude.

    Chris




  7. #7
    Tony Flanders's Avatar
    Tony Flanders Guest

    Default AFOV vs Aperture Poll

    billferris@aol.comic (Bill Ferris) wrote in message news:<20031228220933.19067.00001722@mb-m13.aol.com>...


    Think so? I would agree with you if the dark-sky instrument were, say,
    a 100mm scope. But the best dark-sky subjects are galaxies, and 10x50
    binoculars are simply too small to show any detail in most galaxies.
    Sure, I can *detect* mag 9 galaxies in my 10x50 binoculars under dark
    skies, but that's about the end of it -- they show as featureless blobs
    with averted vision. Which is exactly how those same galaxies would show
    in the 12-inch scope under heavy light pollution.

    But for star clusters, and particularly globular clusters, the 12-inch
    scope under heavy light pollution would have a *huge* advantage. Not
    only do the binoculars not have enough aperture to show globular clusters
    well, they also don't have enough magnification. When stating my preference
    for 10x50 binoculars under dark skies, it was those globular clusters
    that were hardest to give up. M5 is stupendous through a 12-inch scope
    even under very heavy light pollution.

    So where do the binoculars have a clear advantage? Perhaps 4 or 5 very
    large nebulae, like the North America. Perhaps half a dozen galaxies,
    which are big and bright enough to show real detail even in 10x50
    binoculars. But for me, the crowning advantage of the binoculars
    would be for viewing the biggest and best galaxy of all, namely our
    own Milky Way.

    - Tony Flanders

  8. #8
    JJK's Avatar
    JJK Guest

    Default AFOV vs Aperture Poll

    Aperture.

    "Tony Flanders" wrote in message



  9. #9
    Jon Isaacs's Avatar
    Jon Isaacs Guest

    Default AFOV vs Aperture Poll

    >* One person (Jon Isaacs) refuses to take the bait; apples are apples, oranges
    are oranges, and he'll deal with the desert island when and if he has to.

    My solution: Pragmatic, take the 10 inch and buy those Synta 66 degree FOV
    eyepieces for the less than the cost of TV Plossls. Yeah, I know its cheating
    but its what I have done anyway, I am pretty happy with the Synta Ultrawides.

    I am in the position of having both 8 and 10 inch scopes, I have a pretty good
    idea of the difference and it is a tough call because that 50 percent extra
    mirror area is pretty nice but I have gotten used to the wider fields of view
    so viewing through a Plossl seems like looking down a drain pipe.

    Jon









  10. #10
    Kilolani's Avatar
    Kilolani Guest

    Default AFOV vs Aperture Poll

    Make it six... a wide field view of something isn't worth much if you can't
    see the "something" in the first place.

    "starburst" <chills@nonspamming.mail.utexas.edu> wrote in message
    news:bso3ch$3c5$1@geraldo.cc.utexas.edu...
    I'll



 

 
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