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    Re: New compact backup CELNAV system
    From: Gary LaPook
    Date: 2009 Feb 28, 17:22 -0800

    Your version looks very nice, much nicer than mine but I have an excuse.
    The basis for mine were the scales printed out by use of the program
    kindly provided to me by Zvi Doran  so that I could build a working
    Bygrave. I modified this original scale by adding a few tick marks at
    some five minute  points and added more labels for the scale where the
    original labels were far apart. Since I am not a whiz at this computer
    stuff I used a brute force method to add these marks. I added the tick
    marks by hand on a printout of the cotangent scale. I then used a Dymo
    labeler to print out the labels and then stuck them onto the scale. I
    scanned this in, printed out two copies and taped them together and then
    scanned the double wide scale back in. It was a "proof of concept" model
    and it works quite well.
    The one you made looks like you had the help of a computer and it looks
    real professional.  I worked a couple of problems with yours and got the
    right answers so it looks like  you got the scales right.
    I would like to make two suggestions. First, you used the double quote
    symbol ( " ) for minutes and it is usual to use the single quote ( ' )
    for minutes and the double quote for seconds so it would look nicer if
    you changed these marks to single quotes.
    At some points on the scales the ten minute tick marks are too far apart
    making visual interpolation inaccurate.To deal with this problem on the
    one I made, I made the axiliary vernier scale to aid in the
    interpolation since it would have been a lot of work adding more tick
    marks by hand. This complicates the computation whenever you are working
    with values less than ten degrees or more than eighty degrees because
    you have to maneuver this third sheet on top of the other two scales. So
    my second suggestion, if it is not too difficult to get your computer
    program to do this, would be to add tick marks every one minute in the
    areas of the scales above eighty degrees on both scales and also below
    ten degrees on the cotangent scale. This would simplify the computation,
    no need for the auxiliary scale, and would increase accuracy.
    waldendand@YAHOO.COM wrote:
    > Since I'm of the "do it yourself to understand it" school, here are my 
    versions of the Lapook flat Bygrave.  They seem correct, but please check.  
    Still some clean up on labels and tickmarks for large and small angles 
    > >
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