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On Dec 6, 2004, at 7:24 PM, Frank Reed wrote:

> Theory aside, I've got some evidence to throw at this problem. I used
> to live in a twelfth floor apartment within sight of Lake Michigan,
> roughly 120 feet above the lake level. It's a big lake, so there is
> still a true horizon even at that altitude. There were a number of
> other buildings closer to the lake partially blocking the view. One in
> particular, about half a mile away had a line of stonework aligned
> with the lake horizon as seen from my vantage point. But it was only
> aligned on average. I would look at it through binoculars (whenever
> there was a big freighter out on the horizon). Purely for my own
> entertainment, I calculated how much the horizon was moving up and
> down. It was frequently a minute of arc out of line with the average
> and occasionally 2 and 3 minutes of arc. I made no attempt to record
> weather conditions or anything like that. It was just fun to see the
> horizon shifting around from one day to the next. So at that height,
> there IS real variability in observed dip.
> Frank R
> [ ] Mystic, Connecticut
> [X] Chicago, Illinois
>

Sorry, but how were you measuring the difference?

Thanks,

Fred

   

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