NavList:

Dear Bill,
Thank you for your interesting message.

> so I did a ton of IE checks
> using the natural horizon and a smoke stack 5 nm away.  They did not agree
> with sun IE checks, but more on that in another post.

All books I know say that Sun IC checks should be trusted and
not horizon checks.

> I was pleasantly
> surprised with the average (using horizon instead of sun IC), although the
> SD was well below my norm so that disappointed me.

Sometimes the averages are too good by accident.
Especially when the standard deviation is large.

> For the record, sun-derived IC
> (left eye, sextant vertical is 0.4' +/- 0.1',
> horizon IC -0.1 +/- 0.1'

I never did much IC from the horizon (because I rarely see the
horizon in my life), but I noticed that sometimes my
IC from stars differs from IC from Sun
(taken on the same day, and then again next day).
I am speaking of differences of 0.3', sometimes up to 0.6'
In these cases I trust the IC from Sun,
because a) the books recommend it and
b) my Sun observations seem more consistent than star observations.

Alex.


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