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    Re: Using "hack" as a verb
    From: Roger W. Sinnott
    Date: 2018 Nov 29, 21:45 +0000
    Frank wrote >>>>>>. . . Some jargon words in celestial navigation cannot be escaped. My favorite example is Declination. For students new to the subject without a background in astronomy (most students!), this is an odd word with no obvious origin and no connection to the concept behind it. What is the declination of the Sun? It is the latitude of the sub-Sun point. Or even simpler, without too much chance of misunderstanding, it is the "latitude of the Sun". So why say "declination of the Sun" when you can say "latitude of the Sun", employing a word that everyone who passed through grade school has already encountered a hundred times over and understands at least at a basic level? Mostly because it's ubiquitous in the subject. We can't escape "declination", this bit of jargon, because it's everywhere, unavoidable, inescapable. We should define it, emphasize its interchangeability with "latitude", and then use it. That's how I teach.<<<<<<

    I agree with most of this, except it would be better to say (near the end) "...emphasize that it is analogous to latitude on Earth."

    The problem is that in astronomy the declination and latitude of a star or planet are two distinct things.  The latitude (ecliptic or celestial) is the angle measured north or south from the ecliptic, whereas declination is measured from the celestial equator.

    Declination is also confusing because it has other traditional uses.  There's the magnetic declination (variation) of a compass.  And in the case of a wall-mounted sundial, the wall's declination is its deviation in azimuth from facing due south (in the Northern Hemisphere).  Both of these odd uses of declination should be phased out, but not its meaning in the sky.

    Roger

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