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Re: Longhand Sight Reduction
From: Hanno Ix
Date: 2014 Jun 27, 12:40 -0700

Congrats, Francis!

You seem at good spirits. I wish you further speedy recovery.

Let me go back somewhat.

As you know I have answered my own question as to why Bygrave may have chosen
his is particular equations on his slide rule. The answer in a nutshell: He made an excellent choice. The log tan/cot scale is relatively insensitive to reading errors as compared to log cos/sin scales. It is true, the log cos does appear in his equations but any reading errors of it have generally only a minor influence on the end result.
The same is true for versine and havsersine since those are equal to cos/sine plus a constant. Therefore, for my own - future - slide rule for sight reduction I will follow Bygrave's footsteps, too.

This certainly applies to the standard sight reduction. I have no idea if this is also true

for lunars.

In a different vein:
I have been mulling over your description of how to construct Fullers and Bygraves. Obviously, this is still a complicated process. Is there a way to be even more specific?
To give an example: What PVC pipes does one use? Are they irrigation pipes? If so what schedule? Can one buy them at Home Depot/ Lowes etc.? Do you happen to have even the SKU perhaps?

I venture not many CelNav aficionados have your mechanical and PC skills. For them

to successfully tackle such a project they probably need descriptions of the kind the Heath kits were. Remember them? Even if you never had built an electronic device before following them you would end up with a real functioning, useful oscilloscope. However, writing a how-to with so much detail would become a project of its own.

Nevertheless, I put a copy of your description on the wall of my office as an joyful encouragement!

Hanno

On Fri, Jun 27, 2014 at 6:46 AM, Francis Upchurch <NoReply_Upchurch@fer3.com> wrote:

Hi Hanno,
I'm just out of hospital post op, and doing fine. But beached and therefore restricted to sextant readings and playing with slide rules while lying down in the garden overlooking the ocean. Tough life!

Coming round from the anaesthetic, (great for lateral thinking!) I had an idea re the Fuller 2. The main problem is lack of cosine scale, which means I have to convert all cosines to sines first. Simple, but tedious, time consuming and an unecessry source of errors. I never use the log scale on the big fuller 2, so have replaced it with another sine scale,same size ,but with cosine numbers in red and green going the other way. So I can now do all my cosine formulae cel nav calcs direct which halves the time.

I have adapted the minifuller 2 , with the sine scale now having added cosines numbers in red going the other way too. Works ok, but the big fuller 2 replica is more accurate and best for shore based work.
Over the next few days I'll do some comparative LOP calculations using long hand Haversines or Versines, Fuller 2, mini Fuller 2 and Bygrave and see what we get in terms of accuracy and speed. For lunar clearance, I suspect the big fuller 2 will win, but the minifuller 2 probably adequate and more seaworthy and with the Otis King format, a bit faster with less moves.

Best wishes
Francis

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