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Thread: prime focus

  1. #1
    sequalizer's Avatar
    sequalizer Guest

    Default prime focus



    Is the image seen in the camera at prime focus the actual size of the image
    at the
    focal point?



  2. #2
    Wfoley2's Avatar
    Wfoley2 Guest

    Default prime focus

    I believe that pretty well is part of the definition.
    Clear, Dark, Steady Skies!
    (And considerate neighbors!!!)



  3. #3
    Al's Avatar
    Al Guest

    Default prime focus

    The relative size of the image you see in the camera view frame is about the
    size it will appear on film. If you want more magnification, use a
    barlow...but then it's not prime focus.

    Al


    "sequalizer" <EQ@ramalamadingdong.com> wrote in message
    news:Zlr%b.1695$A12.1069@edtnps84...
    image



  4. #4
    tomas's Avatar
    tomas Guest

    Default prime focus



    image


    Yes. Which begs the question, if you can see in good detail what the image
    looks like, say the moon for instance,
    then it means that your optics are doing what they are supposed to. As you
    increase magnification with an EP,
    the light gets spread out more and more, and the quality of the image
    decreases. At some point the image becomes
    a useless blur. The truth is that a well made acromatic lens is as good as a
    well made ED or Flourite one. The only difference
    is the latter puts the whole visible spectrum into the EP whereas the former
    misses most of the blue due to proper
    refractive indices.



  5. #5
    Jon Isaacs's Avatar
    Jon Isaacs Guest

    Default prime focus

    >The truth is that a well made acromatic lens is as good as a well made ED or
    Flourite one. The only difference is the latter puts the whole visible
    spectrum into the EP whereas the former

    I guess the question here is really what is a "good" lens. In my book, a lens
    or objective that has significant false color is not as good one that does not.


    Jon



  6. #6
    tomas's Avatar
    tomas Guest

    Default prime focus


    "Jon Isaacs" <jonisaacs@aol.com> wrote in message
    news:20040226145102.03317.00000357@mb-m23.aol.com...
    or
    lens
    not.


    Not sure what "false color" means. There is nothing false about the visible
    spectrum.



  7. #7
    Jon Isaacs's Avatar
    Jon Isaacs Guest

    Default prime focus

    >

    False color = Chromatic Aberation

    Light from a star is not focused to a single point, commonly associated with
    achromatic objectives which surround bright objects with various "false"
    colors, most commonly violet. Venus in a 80m F5 achromat will display a fair
    amount of "false color."

    jon

    jon



  8. #8
    tomas's Avatar
    tomas Guest

    Default prime focus


    "Jon Isaacs" <jonisaacs@aol.com> wrote in message
    news:20040226164746.01774.00000441@mb-m22.aol.com...
    visible
    with
    fair

    oh, that makes it sensible now.



  9. #9
    Malcolm Stewart's Avatar
    Malcolm Stewart Guest

    Default prime focus

    "tomas" <LA@excite.com> wrote in message news:W_t%b.2059$A12.422@edtnps84...

    Is this a new record for an achromat?

    --
    M Stewart
    Milton Keynes, UK
    www.megalith.freeserve.co.uk/oddimage.htm
    http://myweb.tiscali.co.uk/ms1938/



  10. #10
    Jim's Avatar
    Jim Guest

    Default prime focus

    Malcolm Stewart <malcolm_stewart@megalith.freeserve.co.uk> wrote:


    Bloody hell, you'd need more than an EQ6 to mount *that* bugger.

    Jim
    --
    jim@magrathea.plus.com AIM/iSight:JCAndrew2 - Log in and say 'hi'
    "We deal in the moral equivalent of black holes, where the normal
    laws of right and wrong break down; beyond those metaphysical
    event horizons there exist ... special circumstances" - Use Of Weapons

 

 

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