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    Re: Fata Morgan images set me thinking
    From: Tony Oz
    Date: 2017 Apr 18, 00:39 -0700

    Dear Mark,

    Thank you for bringing this up! I was about to ask a similar question.

    Every weekend I come to the shore to practice the sights, it goes like this: I take 4~5 sights with 2~4 minutes between them, then I do the reductions which takes ~25 minutes. Then I take the next series of sights and so on (until I'm hungry and go for BBQ).

    The conditions three weeks ago on the Finnish Gulf were a sunny day, rather warm air but solid ice covered all the gulf area. The horizon line is uninterrupted within 3 nm from my favorite observation spot.

    All the sights were placing me within 2~4 nm from the GPS position I know.

    Suddenly - all the five sights I took in one series started placing me well 50~60 nm away!

    Puzzled I took the next series of sights - those again put me back to 2~4 nm from my GPS position.

    What was that? Could I make a ~one-degree error reading/writing the measured angle in all five sights in a row? Or was it something with the sudden refraction change?

    Please comment.



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