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    Re: Homemade octant
    From: Greg B
    Date: 2006 Mar 17, 11:01 -0500

    Hi Frank,
            You wrote:
    
        > Pretty cool. What's it made of?
    Thanks, its made of clear white pine & 1/4" finishing lewan(SP?) plywood -
    painted to look like Ebony. I have no idear where you would begin to look
    for Ebony, it is probably $$$ if you can find it and I'm not a good enough
    wood-worker, heck, I'm not a wood-worker by anyones definition. So pine was
    very forgiving.
    
        > How long did it take to construct?
    It took about a month, mostly on weekends.
    
        > Are the scales computer-drawn?
    Yes, I did them in AutoCad
    
        > Have you tested its angular accuracy?
    It seems to be +/- 1 minute of arc. I can't tell where the error comes from
    - but in the end it comes out within +/- 1 min of my MAC.
    
        > (I've got more, but I'll stop for now )
    OK, now I've got one for you: Since the resolution of the scale is 1 min ((
    I was able to do a side-by-side comparison with an actual octant from 1800
    at a local maritime museum , same resolution )) , maybe you can say 30 sec.
    if you hit the "middle" reading on the vernier i.e.;     ||        ||
    but lets say on the avg, to the nearest min. My experiments with running
    the calculations, shows varying the Ho or Lat by 1min can move the AP about
    4 miles. There are different combonations; Ho+ Lat=0, H0+ Lat+, Ho- Lat -,
    etc., etc. some give better results; but 4 miles is a safe number when
    speaking of errors.
    Was this as good as it got ( Talking in period c 1800 if using a octant or
    sextant with this resolution)? and didn't you need to resolve down to 10"
    or  20" to do lunars?
                                                                  -Greg
    
    
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