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    Re: Read the vernier, get the noon latitude
    From: Brad Morris
    Date: 2018 Feb 10, 13:24 -0500
    Hi Bill 

    Begin read a vernier by deciding the base value.  We decide that by finding the nonius.  The nonius can be found on the scale numbered 0 through 20, known as the vernier.  The nonius is the line marked zero.  We see that it is between 73°40' and 74°00' on the arc of the sextant.  Hence the base value is 73°40'. 

    The vernier is marked from 0 to 20, these correspond to minutes of arc.

    Next, we must find the added value.  We  decide that by finding the two lines which best align between the arc and the vernier.  Look across the lines and you will see that the alignment best occurs at either the 13th or 14th division of the vernier, depending upon your persuasion. Count them for yourself.  The 13th line corresponds to 13 arc minutes whilst the 14th line of the vernier corresponds to 14 arc minutes.  The added value therefore is 13 or 14.

    Thus we have
    00°14'  additive

    I hope that helps


    On Feb 10, 2018 2:39 AM, "William A" <NoReply_WilliamA@fer3.com> wrote:

    Gary. thank you. I can see the 40 minutes part better! I thought I understood the vernier part. Now it doesn't make sense.

    I look at the vernier and they line up at 83 degrees. what happens next? do you add that on 40? Thank you, sir. Bill

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