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    Re: Lunar Scopes
    From: Alexandre Eremenko
    Date: 2005 Feb 14, 00:38 -0500

    We already discussed these SNO inverting scopes
    a lot on this list, so let me try to summarize:
    On Sun, 13 Feb 2005, Frank Reed wrote:
    > If I have it right then, the feature that you
    > like about the inverting
    > scopes is not that they're inverting
    > but he fact that they have adjustable
    > alignment (which would make good sense). Yes?
    That it is inverting is not a "feature":-)
    It is just an accidental property, irrelevant
    for astronomical observations. But relevant in binoculars,
    designed for looking at objects on the earth,
    that's why they never make inverting binoculars.
    But from the pure optical point of view, Kepler scopes are
    superior to everything else.
    The features are:
    1. They let maximal amount of light through.
    Because they have the
    minimal possible number of lenses (2) and no prisms or mirrors.
    Probably this is the main advantage. This is also the
    reason astonomers prefer them.
    2. They have no prisms and thus are much smaller and
    lighter than comparable prismatic scopes.
    3. At the same time they have larger field of view
    in comparison with Galileo scopes of equal diameter
    and magnification.
    4. They have wires (you cannot mount wires in a Galileo scope).
    The usefulness of wires was discussed a lot on the list,
    so I do not repeat the arguments. I remember that Frank
    was not convinced in their usefulness.
    5. They have collimation adjustment.
    I don't know why most modern sextants do not have it,
    maybe because for this adjustment you need wires, and it is
    impossible to put wires in a Galileo scope:-)

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