# NavList:

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

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Re: HO 211 (Ageton) sight reduction accuracy
From: Robert VanderPol II
Date: 2016 Jun 14, 09:30 -0700

Paul:

From reading the research papers I could find on Ageton, the accuracy is variable because the tables essentially work as a step function since the results are tabulated for discrete angles. These papers came out about 1940 and are why Ageton suddenly fell out of popularity, navigators realized the limitations of the method and others more accurate and easier to use were becoming available.

Here's an idea you might want to follow: what is average accuracy if values are tabulated at each 0.5° for the range 0°-80° and 0.2° or 0.1° for 80°-90°?

Additionally does the data you have already allow you to plot the 95% or 90% error or whatever percentage error on a graph of Meridian Angle (t) vs. Dec? I envision a family of curves where each curve represents a 90% likelihood that the error is equal to or less than 0.5nm, or 1.0nm, 1.5, 2.0 . . .

I'm thinking of Laidlaw's graph in Bayless 2nd Edition. From the description of the graph the curve represents K=82°/98° and is acknowledged to be a bit arbitrary. This is the dividing line Bayless uses to indicate when Sadler's technique should be used. I am interested in understanding what the likely errors are generally. To this end I was starting to think about how to program something to get this graph. If you have the data are you interested in taking it down this road?

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