NavList:

Bill,

Thank you. I was aware of your and others' brilliant emulators. It would be nice to see if a real ( plastic) 10" rule would work.

Some years ago, whilst concentrating on reducing a sight at sea, using the procedure probably used by my great-grandfather (time sight) I assembled some of the equipment I used.  You can see a home-made paper sliderule, on which I have added a crude haversine scale. My purpose was not to calculate, but to check that various values I was adding up, were in the right range, at the intermediate stages. You can see that I made various errors and corrections en-route.

The paper sliderule served its purpose. There is a world of difference in solo sight reduction at sea whilst keeping a close eye on the boat, and doing it in your computer room at home! I am quite incapable of tabulating and adding up rows of figures, and getting it right first time, whilst also hands-on sailing or flying.

I also worry about the achievable accuracy with a 10" sliderule, as with tha accuracy of Robin Stuart's hand-drawn graphical method. I say this, because Bygrave needed spiral scale lengths of 30 odd feet (30') to get within one minute/mile. No good, a sextant reading in minutes of arc, if the Hc is miles out.

Somewhere on the net I have found a Bygrave emulator. I have experienced the practicality of using a Bygrave solo in a biplane. It works, but I was vulnerable to making a big splash. Don't do that anymore.

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