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    Re: Longhand Sight Reduction
    From: UNK
    Date: 2014 Jul 29, 05:55 +0100

    Thanks Peter,

    Yes, I agree. The only minor problem with my current mini Fuller 2, which is about the same size as the Bygrave, is the compressed scales, designed for the big Fuller, are difficult to read and require magnifiers to get accurate results. I hoped a slightly enlarged Otis King, with original style scales may be easier to read without magnifiers, but yes, the red cosines do clutter the situation a bit. The answer for the big Fuller was to replace the Upper log scale with a cosine scale only. No clutter ,easy to read, just very big slide rule which is fine in my garden but not so good at sea.

    I may first try a re-sized Fuller 2 sin/cos scale, re-sized to Otis King log scale dimension and make a quick prototype to see if it works. If so, I’ll ask Wayne to re-do the scales in the authentic Otis King style with sin/cos scale instead of the log scale.

    This may be a project for the winter.

    Thanks for all your help.



    From: NavList@fer3.com [mailto:NavList@fer3.com] On Behalf Of Peter Monta
    Sent: 28 July 2014 22:51
    To: francisupchurch@gmail.com
    Subject: [NavList] Re: Longhand Sight Reduction


    Hi Francis,


    Many thanks for that. Yes, my Fuller scales were done by Wayne Harrison and look really authentic which is great.(He also did my Bygrave replca scales)The sines are also from 5.8 degree, and no  problem since for LHA, declination,Latitude values,I do  not think I have ever needed trig values below about 8 degrees, so not a problem If I need that, I'll go to my tables!


    Well, ideally the tables would not be necessary---the slide rule should be the complete solution.  I guess the user can do a power-series approximation below 5.8 degrees (using the slide rule for the multiplies of course)---probably only one extra term needed.  Perhaps an almanac can be put on the handle area, which is currently wasted space.

    So in a perfect world Peter, what would be wonderful for a perfect "trig Otis King" would be authentic, accurate scales plus likewise for sines (+cosine numbers in red going in the opposite direction on same scale. I have done that with my Fuller 2 and it works fine).If you do not feel like doing this, would you mind if I ask Wayne to have a go? He is busy at the moment and it may be some time in the future, but I dare say he would accept the challenge of adapting your current scales, making them "authentic" and generating the appropriate trig scale.)


    Sure---if Wayne has an interest he should definitely give it a try.  I've modified my code towards the same end (PDFs attached), but I'm not sure the scale increments and breakpoints are really the best choices, and the style is again "modern" rather than "Otis-King-like".  There's plenty of room for style variations.

    The scales are pretty crowded, and I'm not convinced that the red scales with complementary angles are a net plus on this denser layout---while it relieves the user of jotting down complements, it requires the scale to be kind of reverse-engineered at every reading until one gets used to it.  Putting a full series of red numbers over black would be less confusing, but the text would have to shrink by a factor of 2, which would be unreadable without magnification.


    ps: I can make the source code available, but it contains some inelegant hacks for things like the red coloring.  It really should be rewritten from scratch.

    Attached File:

    (img/128300.otis_king_trig.pdf: Open and save or View online)

    Attached File:

    (img/128300.otis_king_trig_red.pdf: Open and save or View online)

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