NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Homemade octant
From: Greg B
Date: 2006 Mar 17, 11:01 -0500
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 -------------------------------------------------------------------- mail2web - Check your email from the web at http://mail2web.com/ .