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    Re: Ulugh Beg's sextant
    From: Fred Hebard
    Date: 2006 Mar 24, 13:55 -0500

    I can't help you out much with most of your questions, but one
    comment is that the device probably was not a sextant in that it
    probably did not employ the double reflection principle.  I would
    expect it was a sighting tube of some kind, oriented in the north-
    south axis, which could be pointed at various elevations to read off
    the meridian altitude of a star directly.  A quick Google search
    confirmed this conjecture.
    On Mar 24, 2006, at 1:35 PM, Royer, Doug wrote:
    > Ok, I?m now reading a very good book dealing with observatories
    > past and present.
    > There is an interesting chapter on the Samarkand Observatory in
    > Uzbekistan that Ulugh Beg built and used for astronomical
    > observations in the 1400?s.
    > There is a crude description of the FAKHRI SEXTANT used by the
    > Samarkand Observatory that was used to measure the position of
    > thousands of stars to within a few seconds of arc. It has a radius
    > of 120 ft.
    > After a quick search on the web today for pictures or a better
    > description of this sextant I came up dry. There are a few pictures
    > of parts of the observatory but none that are identified as the
    > Fakhri sextant.
    > There is 1 picture of a section of a structure which has 1 vertical
    > stone wall on each side of a center groove and 2 stone tracks
    > running in a vertical arc between the 2 walls on either side of the
    > center groove.
    > I had pictured this ?sextant? as kind of matching how Stonehenge is
    > constructed for celestial observations. But now I?m more interested
    > than ever to find what this ?sextant? really looks like.
    > Frank, because you?re an astronomer, can you help or point me in
    > the proper direction to get a better understanding of what this
    > looks like? Visually or at least a better written description. Or
    > can anyone else help out in this quest?

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