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Herbert and Frank,

Thanks for the explanations, they make sense, and I appreciate your
responses.

Ken
On Jun 22, 2008, at 9:27 PM, Herbert Prinz wrote:

>
> Ken Gebhart wrote:
>
>> Regarding Joel Silverberg's talk on latitude by double altitudes, I
>> asked the question of how this works on the two days of
>> equinoxes.  On
>> these days there will be 12 hours between the zero altitudes of
>> sunrise and sunset at all latitudes.  So how could a unique latitude
>> be determined?
>
>
> Ken,
>
> You are right that the method falters if both observations are taken
> with the body (-ies) at the prime vertical. But this is nothing
> specific
> to either the double altitude method nor to the time of equinox. It is
> simply due to the fact that the altitude of a body in the prime
> vertical
> provides zero information on your latitude, no matter what your sight
> reduction method be and at what time of the year or day the
> observation
> be taken.
>
> But the double altitude method to find latitude is not meant to be
> used
> in that extreme way: One is supposed to take two observations with a
> REASONABLE hour angle between them, say 60 to 90 deg. That always
> works,
> also on the days of equinox. If the hour angle is 180 deg, there is no
> doubt that some triangles degenerate and the method - and any other
> one
> to find latitude - becomes useless.
>
> Did I understand your question and did I answer it?
>
> Herbert Prinz
>
>

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