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It gives you latitude, easily, with minimal calculation, with no need
for a chronometer.

Fred

On Jun 1, 2010, at 12:34 AM, Gary LaPook wrote:

> I've never understood the slavish devotion to catching the sun at
> the exact highest point. If instead you work the noon sight as a
> normal LOP sight using the normal tables (HO 214 etc.) you have a
> four minute period when you work the sight with an LHA of zero and
> an AP within 30 NM of the DR and this method produces an LOP of the
> normally expected accuracy.
>
> gl
>
> George Huxtable wrote:
>> About the method Bligh would have used, to predict the time of
>> local noon based on a morning Sun observation, Frank wrote-
>>
>> "I suspect this trick would be most useful in near-overcast
>> conditions. Though you might not see the Sun enough times to
>> convince yourself that it has reached its peak at noon, if you can
>> look at a local time watch (corrected for the run of longitude
>> from when it was set earlier in the day) then you don't need to
>> see the Sun for more than the ten or fifteen seconds it takes to
>> get a single altitude."
>>
>> =======================
>>
>> Well, it was even more useful than that. As long as the time of
>> noon had been accurately predicted, then an observation of Sun
>> altitude didn't need to be taken right at noon, or even very near
>> to it. It could be taken up to an hour or more either side of
>> noon, whenever a glimpse of the Sun appeared through the clouds.
>> And then, the latitude could be readily calculated from the
>> altitude at that moment, knowing the time difference from noon,
>> using the Ex-meridian Tables. That was primarily what those tables
>> were for.
>>
>> George.
>>
>> contact George Huxtable, at  george@hux.me.uk
>> or at +44 1865 820222 (from UK, 01865 820222)
>> or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.
>>
>>
>>
>>
>>
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