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

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Re: Data from three lunars, with some comments
From: Herbert Prinz
Date: 2003 Jan 15, 18:34 +0000

```Fred Hebard wrote:

> [...]  The apparent distance was cleared for the effects of
> refraction and parallax by Young's method, as laid out by George
> Huxtable last year (I don't think George's implementation of Young's
> method corrects for anything else). [...]

Hello Fred,

For the sake of clarity, it should be said that "Young's method" as described by
George Huxtable (and Cotter) is just a rigorous formula for obtaining D from d,
h_sun, h_moon, H_sun and H_moon. As such, it does not correct for anything per se,
it only puts to work exactly those corrections that you have made in establishing
its input parameters. It is largely a matter of taste how much effort you want to
put into clearing those parameters before putting them into Young's (or anybody
else's) formula.

With approximative clearing methods, it hardly makes sense to apply corrections
that are smaller than the inherent precision of the formula. But since Young's
formula is a strict one, there is no limit to the madness: You could consider
corrections for augmentation of SD moon incl. its correction for latitude, HP of
both bodies, corrections of HP moon for latitude; corrections for refractional
contraction of vertical diameters to apply to apparent altitudes and likewise
contraction of inclined semi diameters to apply to the apparent distance. Even with
all those, the true distance obtained will still not be the true geocentric
distance as tabulated in the almanacs, but that reduced to a point which is the
intersection of the local vertical with the rotation axis of the earth.

Looking at your data, it appears that most of the observed distances suffer from
transcription errors.

For moon/Jupiter lines 4  to the last: Read 52� instead of  53�.
For moon/Aldebaran, from the 2nd line on: Read 68� instead of  69�.
For moon/Sun, for all seven obs. Dist. read 103� instead of  104�.

Best regards and thanks for sharing your experience.

Herbert Prinz

```
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