# NavList:

## A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

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Re: Raw data for bubble
From: Bill B
Date: 2007 Mar 22, 18:48 -0400

```Bill Noyce wrote:

>> I think the intent is to observe until the predicted h occurs, and
>> record the resulting GMT.  From that and the matching LHA you compute
>> GHA and Longitude.  Right?  And you use the graphical method to
>> interpolate to hit the desired h exactly.
>
Bill responded:
> time of transit, he computed Hc.  Any difference between Hc or Ho was
> plotted east/west from AP for longitude.

If understand Peter's method, I missed one part in my answer.  Peter wants
the observation to be exactly at the pre-computed time.  That can be a
problem in practice.  By starting before the exact time he derives two
benefits:

--He has points he can fit to a slope to find for the best estimate of Hs, H
or Ho and identify outliers.

--If he missed an observation at the exact moment, he can locate that moment
on his time axis then the plot line of Hs, H or Hc.

Bill B

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