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Bill, regarding the refraction from temperature  inversion, you wrote:
"I should not be surprised given the range of values  Frank suggested, and the
heat produced by the Chicago metro area and  steel-works, but I was."

It's not the city or the industrial areas. It's  just normal weather.
Temperature inversions are quite common. They have been  associated (in local weather
reports?) with cities and pollution rather by  accident. When a lasting
temperature inversion exists, convection is capped.  This causes a rapid build-up
in ozone and smog. But that's the effect rather  than the cause. Inversions can
occur anywhere including over the open ocean,  especially near major ocean
currents like the Gulf Stream.

"Which brings  us back to coasts and thermal inversions and other
abnormalities.  Not a  rhetorical question--how should the warning label or
guidelines read?   Can it possibly be quantified?"

It *can* be quantified, but it's probably  not worth it. I doubt very many
people use Table 15 or worry about range of  visibility or dip short. As you've
seen, even on this list of navigation  enthusiasts, it's mostly a yawn.

"Also, for non coastal situations, can  modifications to dip etc be adjusted
by some factors?"

Occasionally  over the past 150 years (or more), people have suggested
measuring water  temperature and air temperature and modifying dip values under the
assumption  that the air temperature at the water surface will equal the water
temperature.  It's not a practical solution since the assumption isn't true,
the temperature  measurements have to be accurate, and the improvement in
accuracy is not all  that great.

-FER
42.0N 87.7W, or 41.4N  72.1W.
www.HistoricalAtlas.com/lunars

   

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