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Re: LHA and Meridian Angles
From: Henry Halboth
Date: 2015 Apr 4, 01:53 -0400

Frank,

It may be just techno "bloat", however, astronomically speaking,

LHA, or local hour angle, is the angle at the celestial pole between tha observer's meridian and the hour circle passing through a body measured only westward from the observer's meridian, from 0 to 360 degrees, while ......

t, or meridian angle, is the angle at the celestial pole between the observer's meridian and the hour circle passing through a body measured either eastward or westward from the observer's meridian, from 0 to 180 degrees, i. e. "sundial time"

This distinction may not be relevant to certain sight reduction methods, but imho is relevant to a complete understanding of the various methods of older reduction.

Just my two cents, as they say

Henry

On Fri, Apr 3, 2015 at 3:31 PM, Frank Reed <NoReply_FrankReed@fer3.com> wrote:

Hi Bob, You wrote:
"What is the rationale behind the use of LHA in sight reduction rather than the meridian angle, per se? I am presuming there is either a logical or historical rationale, but can't imagine what it would be."
I think it's just techno 'bloat'. The subject of celestial navigation became HR (highly ritualized) and OOWA (obscenely overloaded with acronyms) in the latter half of the twentieth century, like many military and engineering sub-fields. Everybody wants to sound like a NASA rocket-man, and the English language has been butchered as a result (other languages mostly following in lock-step). Myself, I make no distinction between LHA and t except when specifically teaching or discussing methods that explicitly depend on that distinction. In fact, I avoid "t" completely, if at all possible. I would prefer not to use LHA since acronyms are intrinsically evil. But we are already stuck with GHA and SHA so one more in the same family does no harm, I guess. I try to explain that LHA, for the Sun, is "sundial time in degrees". If the LHA is 45° that's the same thing as saying that the Sun is three hours from the meridian or saying that a sundial would show 3pm (or 9am). Maybe I should use an acronym for "sundial time degrees". Hmmm... STD? No. Bad connotations! I'll stick with LHA.
Frank Reed
ReedNavigation.com
Conanicut Island USA

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