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View Full Version : How come night ecliptic is high when day ecliptic is low



WolfKC
2003-May-15, 02:18 AM
This is a hard question to phrase right, but basically in summer when the sun rises and sets further north, the moon rises and sets further south. And vice versa in winter etc...
I always pictured the ecliptic, the path of the sun as stationary in a perticular day. it only changes over the year by season, further north in summer and futher south in winter (in northern hemesphear summer and winter).
Ok i figure it to do with the earth being tilted and when we are on oppisite side of sun (midnight) then tilt is oppisite of noon. Keeping that thought in mind it seems that at any one day at sunrise or sunset the rise point of the ecliiptic should be the same. But in practical terms I know the sunrise and full moonrise are oppisite of their movement north and south in seasons. Ok that leads me to good reasoning. Full moon is on oppisite point of ecliptic compared to sun.
Still, wish I had a good consise explination with a really good picture that explains it :)
Compare Rise locations (http://www.chipman.org/badastronomy/badastronomy.htm).

kilopi
2003-May-15, 02:46 AM
Sounds like you got it.

The full moon and the Sun are on opposite sides of the Earth. During northern summer, when the Earth is tilted towards the Sun, it will be tilted away from that full moon. In the winter, it reverses. Just like you said.

dgruss23
2003-May-15, 02:47 AM
This is a hard question to phrase right, but basically in summer when the sun rises and sets further north, the moon rises and sets further south. And vice versa in winter etc...
I always pictured the ecliptic, the path of the sun as stationary in a perticular day. it only changes over the year by season, further north in summer and futher south in winter (in northern hemesphear summer and winter).
Ok i figure it to do with the earth being tilted and when we are on oppisite side of sun (midnight) then tilt is oppisite of noon. Keeping that thought in mind it seems that at any one day at sunrise or sunset the rise point of the ecliiptic should be the same. But in practical terms I know the sunrise and full moonrise are oppisite of their movement north and south in seasons. Ok that leads me to good reasoning. Full moon is on oppisite point of ecliptic compared to sun.
Still, wish I had a good consise explination with a really good picture that explains it :)
Compare Rise locations (http://www.chipman.org/badastronomy/badastronomy.htm).

Ok, I'll give this one a go. The link below gives some nice sky charts. The ecliptic is the curving line on the plot the has a wave appearance.

http://observe.phy.sfasu.edu/SFAStarCharts/SFAStarChartsAll.pdf

The celestial coordinates are right ascension(RA) and declination(DEC). Think of RA like longitude and DEC like latitude. Lets say your latitude on Earth is 45 degrees. For objects on the ecliptic the higher the declination the higher the altitude that object will be in your sky. Now on June 21 the Sun has a DEC of +23 degrees - so that is when it reaches its highest noon time altitude. On December 21, the Sun has a DEC of -23 degrees so the Sun reaches its lowest noon altitude.

Now the full Moon occurs when the Moon is on the opposite side of the sky as the Sun. For a full moon in the summer when the Sun is at +23 degrees DEC, the Moon will be at the point on the ecliptic where the Sun would be in the Winter on December 21 (-23 deg DEC). So in the summer the noon sun is high and the full moon is low. In the winter it is just the opposite.

I'll stop there, but if that doesn't give the answer you're looking for fire away some more questions. Hopefully I can help.

ToSeek
2003-May-15, 02:55 PM
Try this image:

http://www.astro.columbia.edu/~archung/labs/fall2001/images/sun_year.jpg

When the Sun is at the summer solstice position, the Full Moon is at the winter solstice position. Now imagine this whole image rotating around a line through the celestial poles (as in fact it does). When the summer Full Moon is high in the sky, it will be on the right but at the same angle below the celestial equator that it is on the left. So to a viewer in the northern hemisphere it will be low in the sky.