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    Re: Degrees and minutes vs decimal degrees and theDaily Pages
    From: Geoffrey Kolbe
    Date: 2015 Oct 19, 18:15 +0100




    On Mon, Oct 19, 2015 at 3:37 PM, Brad Morris  wrote:

    ​As an​
     interesting side note, you never have to remember to approach contact in the same direction with a vernier.  The tangent screw does not provide the reading, and as such, gear lash is irrelevant.  With a micrometer drum, you do.

    ​Quite so​
     

    In principle, there is no doubt that vernier will be more accurate than drum. A vernier is a direct reading of the position of the index arm against the arc. 

    A micrometer drum sextant is easier to read, but the assumption is that the thread on the tangent screw is uniform and free of errors (on both sides of the thread), that it is free of backlash, that the index arm is free of flexure, or side movement​ - which depends on the tapered journal bearing on the index arm be perfectly tight, etc. That requires a much higher level of technical excellence than is required in a vernier sextant.

    Geoffrey Kolbe
       
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