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    Re: Homemade octant
    From: Robert Gainer
    Date: 2006 Mar 17, 11:40 -0500

    You can get Ebony from M.L. Condon, 250 Ferris Ave in White Planes New York. I 
    use their operation in Stormville, New York to get some of the wood we use in 
    our boatbuilding program. And yes, it will cost you.
    Robert Gainer
    
    >
    > From: "cfi@licfi.com" 
    > Date: 2006/03/17 Fri AM 11:01:04 EST
    > To: NAVIGATION-L@LISTSERV.WEBKAHUNA.COM
    > Subject: Re: Homemade octant
    >
    > 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
    >
    >
    > --------------------------------------------------------------------
    > mail2web - Check your email from the web at
    > http://mail2web.com/ .
    >
    
    
    

       
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