NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Homemade octant
From: Robert Gainer
Date: 2006 Mar 17, 11:40 -0500
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/ . >