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    Re: Making an impact with hav-Doniol
    From: Gary LaPook
    Date: 2015 Jun 20, 17:11 +0000
    First, the presentation needs to be more polished 2nd, the azimuth computation needs to be eliminated, it makes the very elegant short solution for altitude appear much more complicated and forbidding and will scare people away. 3rd, the diagram needs to have each scale repeated, top and bottom, right and left to make it easier to visualize the lines from those scales to the curves. 

    The Hanno diagram is much easier to use than the Rust diagram which has too many lines and curves and you need the eyesight of a teenager to use it. The Hanno diagram is simpler, not cluttered and, this is important, accurate enough for real celestial navigation. Remember, the Doniol method is used with the DR as the AP so the intercepts are much shorter than when using precomputed tables like HO 249, HO 229, HO 214, HO 218, and also shorter than when using trig methods like HO 208 and Weems since all of those methods require AP's spaced by whole degrees of latitude and LHA so the azimuth does not need to be as precise as when using those other methods.

    To avoid drawing lines on the diagram simply use two cards or pieces of paper to establish the two points on the curves and to take out the azimuth. One card with one edge on the top scale with the other edge on the right scale, the corner establishes the point on the curve. The other card has an edge on the scale on the left with the corner placed on the curve established by the corner of the first card then read out the azimuth with the edge of the second card on the bottom scale. No drawing on the diagram.


    From: Greg Rudzinski <NoReply_Rudzinski@fer3.com>
    To: garylapook@pacbell.net
    Sent: Saturday, June 20, 2015 9:26 AM
    Subject: [NavList] Re: Making an impact with hav-Doniol

    The graph reduces reduction time by at least two minutes with less chance of error. Other sight reduction methods also benefit from the graphical azimuth solution - Classic Trig Log, Ageton, Dreisonstok, and Weems. The Weems Line of Position short table uses the Rust diagram for azimuth. I like the Ix graph better than the Rust diagram. Why are you marking on the graph ? No need to do that. The Hav-Doniol azimuth formula is just a back-up for the graph. The long division step is what shoots the formula down for practical use.
    Greg Rudzinski

    From: Sean C
    Date: 2015 Jun 20, 01:44 -0700
    I am just now beginning to look into this method of sight reduction. (Work and home life have kept me from them until now.) I must say, at first I was reluctant to learn a 'new' method, no matter how simple. Especially one that required two different sources for altitude and azimuth. (The haversine calculations and Hanno's diagram.) But, after re-reading all of the posts on the topic, I saw the haversine azimuth formula mentioned in a couple of posts. At first glance, it all seems simple enough. Even the azimuth rules appear identical to the rules for pub. 229, which I have already memorized. If this method were indeed adopted by HMNAO, my only wish is that the azimuth formula would be included. No offense to Hanno, I haven't even tried the diagram yet. But it seems to me that using it in a format like the N.A. would require lots of drawing (and erasing) on the page, perhaps affecting the diagram itself. (Not to mention my slightly obsessive aversion to writing and/or drawing directly in any of the books I own.* Emergencies notwithstanding.) I suppose one could just use the corners of a sheet of paper, or any other handy right angled object to acomplish the task, but as I said, I haven't tried yet.
    Speaking of the concise S.R. tables though, aren't they actually one of only two contributions made to the N.A. by the Nautical Alamanac Office of the USNO? My almanacs state that: "Copyright for The Nautical Almanac is held by the U.K. Hydrographic Office..." and "The following U.S. government work is excepted from the above notice [...] pages 6 and 7 [solar eclipse diagrams], and pages 286-315. [the main concise S.R. tables]" So, perhaps the Hav-Doniol method should be submitted to the USNO, who may then submit the idea to HMNAO? I don't know. Thoughts, anyone?
    *I know, I'm weird. :)
    Sean C.
    If the N.A. route does not pan out, you can add my vote for "Hav-Doniol, Will Travel". That phrase also popped into my head as I was searching through the posts about it here.

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