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

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Re: Doniol for time sight reduction?
From: Greg Rudzinski
Date: 2015 May 15, 12:12 -0700

Francis,

The most elegant time sight formula to try and modify to all haversines would be the formula used in Rust's 1918 Practical Tables for Navigators and Aviators.

hav t = (Cos (Lat. ~ Dec.) - Sin Ho) / 2 Cos Lat. Cos Dec.

~ same name (Lat. - Dec.)    ~ contrary name (Lat. + Dec.)

If Lars is watching then maybe he can work up something that will look good.

Greg Rudzinski

From: Francis Upchurch
Date: 2015 May 15, 07:59 -0700

Question for I think Hanno +/-Greg.

Could the Doniol method be adapted for the Time sight reduction? I've been playing around with Fuller slide rule using the cosine formula

cos(LHA)=[sin(alt) - sin(dec)·sin(lat)]/[cos(dec)·cos(lat)].

Works fine but takes longer than LOP (Hc) using Bygrave or Brown-Nassau.

I like the old 19th century methods using trig logs and haversines, the formula I have is hav.LAT=logsec.lat+logcsc.p+logcos.s+logsin(s-alt). where p=polar dist and s=1/2sum. I would be interested to know if Doniol could do it?

Best wishes

Francis

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