Next message: Frank Reed: "Re: Homemade octant"
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: "" <>
> Date: 2006/03/17 Fri AM 11:01:04 EST
> To:
> 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 <g>)
> 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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