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    Re: Question about old sextant
    From: Peter Monta
    Date: 2018 Jan 25, 11:29 -0800
    Hi German,

    Beautiful instrument.

    That part is called a "back sight"---it's used for measuring angles larger than the "forward mode" or "normal mode" can handle.  See Figure 5b on this page:

    I'm not too clear on why this attachment fell out of favor.  Large angles can also be reached with auxiliary prisms, which might be one reason, or that a telescope for this mode is awkward to mount and use.

    Cheers,
    Peter

       
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