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    Re: Daytime Venus Rising Dip Short
    From: Gary LaPook
    Date: 2012 May 6, 02:11 -0700
    They are only in the Kollsman instruments. They don't actually cross, there is a gap in the center. I believe that they are there to help you keep the bubble near the center for most accurate sights. In the periscopic instrument that  fits in a mount, the vertical line allows you to aim the sextant at the pre-computed azimuth so that you can find the desired body, the navigators field of view is limited to what he can see through the sextant, no windows. this also allows him to measure azimuths and check the deviation of the compass while in flight.

    See this picture that i posted a couple of years ago.

    http://fer3.com/arc/img/114221.img_6428.jpg

    http://fer3.com/arc/m2.aspx/Kollsman-periscopic-sextant-mount-LaPook-oct-2010-g14221

    gl

    --- On Sun, 5/6/12, Geoffrey Kolbe <geoffreykolbe---.com> wrote:

    From: Geoffrey Kolbe <geoffreykolbe---.com>
    Subject: [NavList] Re: Daytime Venus Rising Dip Short
    To: NavList@fer3.com
    Date: Sunday, May 6, 2012, 12:22 AM

    At 05:59 06/05/2012, GL wrote:
    > I have attached two photos. IMG 8895 is a view through the Kollsman periscopic sextant and 8887 is a view through my Pioneer A-7.


    Why do these instruments have cross hairs Gary?

    Geoffrey




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