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Brad,

I can't speak for a MHR-1 only for a 10" slide rule. There are problems reliably working the rule when going to weather on a small craft. It took me over 15 minutes to complete and then the result was untrustworthy. The 5 place haversine table takes 5 minutes with a confident result. Time extracting LHA, declination, and for plotting are not included in reduction times.

Greg Rudzinski  

From: Brad Morris
Date: 2015 Jul 11, 14:08 -0400

Hanno

You may wish to examine Mr. LaPook's version of the Flat Bygrave.  The mechanical objections to the cylindrical Bygrave you raise are obviated.

If there is a choice between a series of hand and paper calculations or some manipulation on a Bygrave (of either cylindrical or flat type), hands down the Bygrave wins, IMHO.  Its far superior to a series of computations performed by hand, as arithmetic errors are all but eliminated.

The Bygrave is accurate and fast.  1'-2' accuracy in less than 2 minutes of time?   Combine with low chance of arithmetic error?  No contest. 

I've not seen any disclosure or publication of the time it takes to perform Hav-Doniol.   Perhaps the more experienced practitioners would divulge the elapsed time??

Of course, I am biased.  I have an MHR-1.  That's superior to the Flat Bygrave as the angle between the scales is automatically maintained, just as in a Fuller or Otis cylindrical rule.  The MHR-1 also has a superior locking mechanism to a cylindrical Bygrave.  Beautiful instrument but an expensive device.   (The expense has driven the reproduction effort and indeed Gary's inventiveness).

This isn't a knock on the Hav-Doniol reduction method.  In a recent note, you compared Hav-Doniol to the Bygrave, and came to what I feel is an erroneous conclusion. I herein question that conclusion.

Brad