A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Francis Upchurch
Date: 2016 Feb 21, 22:34 -0800
NEW Fuller 3 (CN. AHA) Slide rule for CelNav. My ultimate Cel Nav slide rule?
Following the interesting discussions in January, especially with Bob, Brad, Gary, Hewitt et al , I've made some major modifications to my trusty old Fuller 2.
1) Extra Cos/sin scale on the innermost tube which was devoid of scales in the original, just carrying the moving brass curser and index A and B. This still does that, but in addition moves the cos/sin scale directly against the identical second cos/sin scale on the middle tube, allowing direct multiplication and division of sins and cos without having to go via the C/D outer scale.
This in response to Hewitts idea with his combiantion slide rule and Brad's "AHA" moment.
2) replaced the unused Log scale with a scale of Tangents. There is only room for one of these, so I still have to go via the C/D scale to multiply or divide tangents.
Early test drive indications suggest it works perfectly for doing Hc and Az using the cosine formulae with about a third reduction in movements compared to the previous method involving the C/D scale. I'm next going to compare with Bygrave and BN. And also try using Bygrave formulae as per Gary's intructions.
I've also done 1 lunar clearance using the Karl cosine formulae and got perfect result as per calculator.
In the "expanded" part of the scales, it seems to read to 5-10 seconds of arc and a minimum of 30 seconds on the compressed ends.
This now seems to be my near perfect dedicated CN slide rule, which still retains almost all the funtionality of the original Fuller (minus the unused Logs, I've never needed on a slide rule).
Details /photos on request.