# NavList:

## A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

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Proportional Logarithms
From: Hanno Ix
Date: 2015 Feb 27, 19:56 -0800
Henry,

what exactly are proportional logarithms,
what specific problems do they solve
and how does one use them?

Also it seems there were abandoned - why?

Is there anyone else who knows?

Thanks!

H

On Fri, Feb 27, 2015 at 7:41 PM, Henry Halboth wrote:
Francis,.you wrote,

"Also, intriqued by the possibility of reducing lunars by purely graphic means. Could you show me an example if this can be done?"

At the risk of incurring Frank R.'s ire, I attach a proposed method of clearing a Lunar Distance by part graphical & part mathematical means. There is really nothing much new in navigation - it's just a matter of knowing where to look! It goes without saying that I have not tried this method and present it purely as a matter of possible interest.

Henry

On Thu, Feb 26, 2015 at 5:06 AM, Francis Upchurch wrote:

Robin,

that is interesting!

I'm no mathematician, and don't really  understand simple numbers, never mind complex ones! However, am I right in thinking that if you had sterographic projection charts (flat), you can place circles of equal altitudes directly on this and get a fix with 2 intersections? i.e, like using the big globe idea, but instead using flat (stereographic) charts? Is that correct? If so, any advice on where to get stereographic charts to do this?

Also, intriqued by the possibility of reducing lunars by purely graphic means. Could you show me an example if this can be done?

This could save me a lot of engineering work. was thinking about building a globe to do this! would rather use stereographic charts if feasible.

Best wishes

Francis

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