NavList:

OK, I guess this is the message that might get me back to being a more active poster and give me a chance to see if I know how to use the current system.

Back when I was a more active participant in the list (in 2002)I asked the following question:

Has anyone seen or used a Poor Line of Position Computer? Of all the mechanical
devices described in Bowditch in the history of sight reduction section it
appears to have been a device that should have been popular. For anyone not
familiar, it's described as a circular slide rule device with multiple rings
that could solve the cosine haversine equation to a tabulated accuracy of 10'
with further interpolation possible. It's not clear however just how big one is
or whether they were ever very widely used. I can't help but wonder if they
would have been more popular had the inventor Charles Poor not chosen to market
the device under his surname.

Chuck Griffiths
(I'll also note that in those days, I think most of us always signed our posts with real names.)

That posting went unanswered for several years. Later, during a time I lost track of the Navlist when it was switched to Google groups, waldendand--com (who I believe may be Dave Walden) made some great posts starting with message 6273. He answered the question of how big they were (about 15 inches in diameter) and gave instructions about how to make one of these devices and posted a link with detailed instructions on their use.

I am still interested in the question of how popular they were in their day. Knowing a little more about the device it appears that they should have been useable as a quick sight reduction method that had reasonable accuracy for air navigation or mid ocean positions on a small boat. I hope that Ward Poor will turn out to be a relation of Charles Poor and he might be able to tell us whether they were ever sold in any great number and whether Charles Poor was aware of any niche in navigation where they caught on. Charles Poor was apparently a very accomplished yachtsman but he believed the device would be most useful in air navigation.

Chuck Griffiths
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