NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: UNK
Date: 2014 Nov 12, 18:58 -0000
Hi Greg,
Totally agree with you. Congratulations to you and Hanno for what I believe is the best longhand system ever. My emotional attachment to slide rules may not be entirely logical, but still my preferred option.
I will continue to use both. Bye the way, a few years ago I went “absolute minimalist” , just doing meridian passages for latitude and alts 1 hour before LAn and then set sextant to same alt to get after lan, to estimate LAN for longitude. Nothing other than Eot and Dec tables needed and no LOP calculations. Usually gave accurate lats and longs +/- 10-15 Nm.
PS, like your sand glass! Amazing that Cook et al still using them for dead reckoning! Don’t think they would give accurate longitudes though? Great fun though. I use a water clock in my lunar “no clock” fixes (lunar times then sun/lunar fix, with water clock time difference between alt obs. It works! You do not need an accurate clock to get longitude!)
Francis
From: NavList@fer3.com [mailto:NavList@fer3.com] On Behalf Of Greg Rudzinski
Sent: 12 November 2014 16:21
To: francisupchurch@gmail.com
Subject: [NavList] Re: Longhand Sight Reduction
Francis,
I am in total agreement with you on avoiding interpolation where possible. Two thumbs up on the 2' table :) A few additional benefits of the haversine Doniol table. There are no special rules for L+d > 90° or LHA Meridian Angle > 90° and the majority of observations (especially the Sun) can be reduced from the same side of the haversine table vs. page turning of other methods. After a week of trials it has become clear that this is the best short table sight reduction method that uses the DR position as the assumed position. I have a shelf of sight reduction tables that will now be collecting lots of dust ;-)
Greg Rudzinski
P.S. The 8" circular slide rule does almost as good a job on the multiplication step as the Ottis King.
From: Francis Upchurch
Date: 2014 Nov 11, 23:35 -0800
Many thanks Greg,
My original confusion resulted from missing Hanno's posting of Nov 5th re the Hv only formula. Now I've found it. Congratulations to Hanno for this and his 2'Hv table which I find eaiser to use than your 10' table.(I keep making mistakes with interpolation).
I have test driven your e.g. using the Doniol, and compared it to Bygrave, and other slide rules (using cos formula, not Doniol).
Please see attachments if interested.
I'll certainly put your/Hanno's Doniol (Hv) into my minimalist crash bag, but also the Otis King+sin table.
If space is not a problem, I still prefer the Bygrave, with my prototype minifuller 2cos a close second.
Keep up the good work both.
Best wishes
Francis Upchurch
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