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## A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

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Re: recommendation for slide rule ?
From: Greg Rudzinski
Date: 2009 May 24, 11:14 -0700

```The Pickett N3-T virtual slide rule works well. I was able to solve
the Hc altitude formula to three digits but to get the inverse sin I
went to Bowditch table 31 (natural trig functions). Slide rule purists
will cringe but this is a simple practical way to overcome the 10"
slide rules poor inverse sin scale resolution for calculated altitudes
above 30 degrees. The WW 2 PBY Catalina navigators may have used
similar tricks to accommodate the 10" slide rules they favored.

On May 21, 4:00�pm, Paul Hirose  wrote:
> Greg Rudzinski wrote:
> > Gary,
>
> > � � �It does appear as you have illustrated that the K&E 4080 has
> > multiple advantages over the Pickett.
>
> The K+E 4080 family has the disadvantage that its rear (trig) side lacks
> a C scale. While you can easily do 2 * sin 20�, or 2 / sin 20�,
> something like 2 * 3 or 2 / 3 requires flopping the rule to the other
> side. Also, if you simply want to read the value of sin 20�, you must
> first align the S and D indices.
>
> Like most high-end rules, the Pickett N3 you mentioned has scales C and
> D on both sides of the rule, eliminating the above annoyances. Scale S
> is not adjacent to D as on the 4080 family, but this is a matter of
> taste rather than computational power.
>
> The Pickett N3 is one of the few rules with a double tangent scale.
> This doesn't give the rule any greater accuracy or range, but sure makes
> life easier when dealing with tangents and arc tangents.
>
> Lest anyone think I'm a Pickett shill, let me say the only slide rule
> I've ever liked enough to buy two identical ones is the 10 inch K+E
> 4181! It's a nice competent workhorse with everything I need but no
> frills. The shortcomings I pointed out above are charming blemishes.
> Part of the fun is working around them. However, if using a slide rule
> were just a job, I'd rather have an N3.
>
> I believe the Pickett "Eye-Saver" yellow was just a marketing gimmick.
> It's not any easier to read, and I find a white rule more attractive. As
> far as I can tell, readability is a tie.
>
> Note the Pickett doesn't necessarily mean yellow. Their high end rules
> were all available in white. You'll find them on eBay, but expect to pay
> more because they're less common.
>
> As far as I know, Pickett trig scales were always marked in decimal degrees.
>
> On the following simulator you can use a (white!) Pickett N3 to work
> Gary LaPook's sight reduction example. Just drag the slide and cursor to
> make the settings. The only difference is that where he says to "line
> up" the S and D scales (bring their left and right indices into
> coincidence), you use C and D.
>
> http://www.antiquark.com/sliderule/sim/n3t/virtual-n3-t.html
> (The virtual slide rule requires that Javascript be enabled. After the
> page loads, it's self-sufficient, requiring no Internet connection.)
>
> Note that Gary's azimuth computation has a mistake. The message text
> says to set the cursor to cos 14�, but the picture and the final result
> indicate it was set at cos 20� instead.
>
> Hein Bodahl wrote:
> > The Faber Castell 2/83, or even better the FB 2/83N Novo Duplex, is by
> > some said to be the best ever made. It is a desktop model of double
> > length. Unfortunatly that makes it sensitive to temperature changes (or
> > so "they" say).
>
> The famous Novo-Duplex, the so-called "ultimate slide rule", is dear to
> collectors. But I wonder how many of these just sit in display cases.
> They are so collectible, I'd hesitate to put one to work at home, never
> mind take it to sea on a small craft.
>
> Recently I bought a Faber-Castell 63/82, which has several of the same
> features:http://www.sliderulemuseum.com/Faber/P030_Faber-Castell_63-82_Biplex.jpg
>
> It looks impressive, but in actual use the 63/82 is cluttered and
> gimmicky. Those auxiliary hairlines are the worst part. They're hardly
> ever useful, and all those extra lines make it hard to read the scales
> quickly. And the slide has too much friction and stick slip. Its feel is
> the worst of any of my plastic rules.
>
> To be fair, I grew up with American slide rules. Fancy features like
> extra hairlines, Pythagoras scales, etc. have never been popular here.
>
> Not that we always know better. One ridiculous practice, common on
> American rules, is to chop off all scales to exactly the same length as
> C and D. Look at the left end of ST in that N3 simulator. Wouldn't it
> make sense to carry the scale down to .56�? The K+E 4080 family has the
> same problem.
>
> As the picture of the Faber-Castell 63/82 shows, German makers often
> extend such scales a little to end them at a sensible graduation.
>
>
>
> ns...@hotmail.com wrote:
> > British brand UNIQUE offered several sliderules of cheap
> construction, but
> > interesting scale layouts. Among them was so called "Unqiue
> > addition to normal log scales it featured sine and tangent scales
> located both
> > on slide rule body AND slide. Allegedly this would make certain trig
> > calculations easy.
>
> That's true. For example, to compute sin A sin B on a rule with trig
> scales on the slide only:
>
> 1. Align the indices, i.e., center the slide so the C and D scales coincide.
>
> 2. Set hairline to A on scale S.
>
> 3. Pull C index under the hairline.
>
> 4. Set hairline to B on scale S.
>
> 5. Read product on D at hairline.
>
> But with trig scales duplicated on slide and body, step 1 is unnecessary
> if you use the S scale on the body for step 2.
>
> --
> I filter out messages with attachments or HTML.
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