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(no email)
Date: Fri Mar 17 2006 - 11:01:04 EST
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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