Talk:Declination
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In the Southern Hemisphere, because our seasons are switched is the formula for the declenation of the sun now:
d = +23.45 * cos(360/365 * (N +10)) ?
Is the Sun Dec now -23°27' at the Southern hemisphere summer solstice and +23°27' at the Southern hemisphere winter solstice?
no, it's just a matter between the sun and the earth, dec is + when the sun is overhead in the northern hemisphere (northern summer, southern winter) and dec is - when the sun is overhead in the southern hemispere (southern summer, northern winter). hope that helps...
- FourBlades 19:48, 26 July 2006 (UTC)
Hello, The "more precise formula" requires one to know the fractional year. For this quantity, N is required. Is this really the same as N in the previous paragraph? If so, then this formula appears to be much less accurate then the linked table. Can anybody add a comment on how accurate that formula is? Thank you, Roger Jeurissen.
- The Spencer formula is more accurate than the top formula, but indeed is somewhat less accurate than the linked table. I wouldn't say "much less accurate" though. For example, on Oct 15 of a 365 day year, the first formula gives a declination of -9°30'; the Spencer formula gives a declination of -8°11'; and the table gives a declination of -8°18'. I did these calculations in Excel 2003, but I did notice that the the first formula gives a value opposite in sign to that given by the Spencer formula or the linked table. --Rpresser 20:38, 31 October 2008 (UTC)
[edit] Dubious
The following statement is dubious:
- The Moon also has an annual cycle, with maximum declination at northern hemisphere midwinter and minimum at midsummer.
- This statement is only accurate for the full moon. At other times of the lunar month, the Moon reaches its highest declination at different times of the year.
- The statement should be reworded in a more globally-neutral manner. The full moon would appear highest in the sky closest to the winter solstice and at its lowest closest to the summer solstice - and this statement is true regardless of hemisphere, or which winter or summer solstice is being considered here. From an equatorial perspective, the most northerly full moon is the one closest to the southern solstice, and vice versa. -- B.D.Mills (T, C) 04:19, 19 June 2008 (UTC)
[edit] When the moon runs the highest and lowest:
- Around Mid-winter, the moon runs the highest when in its waxing gibbous phase, and the lowest when in waning crescent.
- Around the spring equinox, the moon runs the highest when its around first quarter (waxing half-moon), and the lowest when it's around last quarter (waning half moon).
- Around mid-spring, the moon runs the highest when in its waxing crescent phase, and the lowest when in waning gibbous.
- Around the summer solstice, the moon runs the highest when it's around the new moon, and the lowest when around the full moon.
- Around mid-summer, the moon runs the highest when in its waning crescent phase, and the lowest when in waxing gibbous.
- Around the fall equinox, the moon runs the highest when its around last quarter, and the lowest when it's around first quarter.
- Around mid-fall, the moon runs the highest when in its waning gibbous phase, and the lowest when in waxing crescent.
- Around the winter solstice, the moon runs the highest when it's around the full moon, and the lowest when around the new moon.
There is a bit of variation, regarding the exact points that the moon runs the highest and lowest each time the moon orbits Earth. This is because the moon's orbit deviates slightly from the ecliptic. However, since that deviation is less than 1/4 of Earth's axis tilt, Earth's tilt is strongly the dominating factor. Therefore, the above generalizations are always at least close to actuality.
I'm not sure if there's a word that is used to identify the moon's highest and lowest declinations for each time it orbits Earth. However, I think that "lunastice" would be a good word, because it replaces the "sol" (Latin for sun) in "solstice" with "luna" (Latin for moon). I also think that it would be better to use the words "high" and "low", rather than "summer" or "winter", with "lunastice", because the moon's declination, of course, doesn't dictate the seasons like the sun's does.
