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The N.A. states that the table allows for a S. D. of 16' and a
refraction of 34' (the value in the refraction table for zero altitude)
so the Ho is actually -50' when the UL is on the horizon when observed
from sea level. To this you would also have to allow for dip.

gl



Apache Runner wrote:
> The typical correction at the horizon is around 30-some odd arc
> minutes for refraction at the horizon.   The sun appears to be higher
> in the sky than it really is.    So, that means that the sun is
> visible after it has "set".   You would have to take a slightly
> earlier time for sunset - say when the lower limb is 15 arc-minutes
> above the horizon (since the diameter of the sun is approx. 32
> arc-minutes).
>
> Or something like that....
>
> On Thu, Feb 4, 2010 at 4:32 PM, Marcel Tschudin
> > wrote:
>
>     Jeremy, I would like to give it an other try using the GPS data. What
>     was the latitude, or did I miss it? Marcel
>
>
>
>

   

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