A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Hanno Ix
Date: 2014 Nov 12, 19:09 -0800
One more question (oh, apologies for the typos, for “break” read brake!. Going senile). Please give information on 8 inch circular slide rule. I know nothing of these but plan to build a “Poor” 12inch one day. (see my previous postings on this. An LOP slide rule pre-dating the Bygrave).The Otis King is very compact and surprisingly accurate for the relatively short length of the scales.( I get 3-4 decimal spaces routinely with the O.K ,but 5-7 with the Fullers which have much longer scales.) I suspect some of that is down to the shear quality of construction. The best I have seen in any cylindrical slide rule.(my Otis King is a superb piece of engineering.)
Anyways, keep up the excellent work.
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 ;-)
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.