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    Re: Aligning a transit telescope to the meridian
    From: Geoffrey Kolbe
    Date: 2008 Apr 22, 07:01 +0100

    Hello Greg
    
    Well, as I indicated, Polaris at these latitudes is a bit of a problem,
    having an altitude of 55 degrees (my latitude) and in the wrong direction.
    
    Firstly, the siting of the telescope would have to be a semi-permanent
    arrangement and would have to be arranged so that it has a good view of
    Polaris as well as to the South, and it would have to be high enough that I
    can get at the eyepiece when it is tilted at 55 degrees. These are quite
    severe requirements in an otherwise reasonably simple construction. I can't
    just set it up in the basement looking out of a South facing window.
    
    Secondly, the error in measuring the azimuth of Polaris (or any other body)
    goes as the East/West tilt error in the telescope standing axis times the
    tangent of the altitude. As Tan(55 degrees) is about 1.42, my resultant
    error in setting the telescope on the meridian would be at least half as
    large again as the tilt error in the standing axis of the telescope. I
    would prefer to use lower bodies if possible to minimize this error.
    
    Geoffrey Kolbe
    
    >I'm not sure how a transit telescope is aligned in the real world, but
    >how about using Polaris to establish a true north/south line (with the
    >appropriate corrections from an almanac, etc.), then using something
    >like a surveyor's rod setup on the south side of that line to setup the
    >'scope facing true south?
    >
    >Sounds like an intuitive solution to me, at least...
    >
    >--
    >GregR
    
    
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