Confused by today's APOD description of the moon S. position

Comments and questions about the APOD on the main view screen.
tanq10
Asternaut
Posts: 6
Joined: Mon Jun 20, 2005 10:51 pm

Confused by today's APOD description of the moon S. position

Post by tanq10 » Thu Jun 23, 2005 8:44 pm

Today's APOD talks about the sun's northern most position in the sky, marking the summer solstice. But I'm confused as to why the moon, also moving near the ecliptic, is described as rising the farthest south for the year:

"the full Moon rising near the ecliptic plane opposite the Sun was at its farthest south for the year."

If near summer solstice the Sun, moving through the ecliptic, rises and sets the furthest north for the year, why then does the moon, moving very near the ecliptic, not also rise the farthest north for the year??

Link to the APOD page: http://antwrp.gsfc.nasa.gov/apod/ap050623.html

Curious,

Will

William Roeder
Ensign
Posts: 59
Joined: Thu Jun 16, 2005 3:46 pm

Post by William Roeder » Fri Jun 24, 2005 2:54 pm

Since no one tried to answer this, I'll take a shot.
I'll assume the moon is near the ecliptic as you do.
If it is a new moon, thus being on the same side as the sun, then it would also be farthest north.
Instead if it's a full moon, opposite the sun, it would be farthest south.

Try a drawing: (sun) (\) (moon)

tanq10
Asternaut
Posts: 6
Joined: Mon Jun 20, 2005 10:51 pm

Still don't get it

Post by tanq10 » Fri Jun 24, 2005 7:38 pm

Thanks for answering!

Hmmm.. Yes, the sun and full moon are on opposite sides of the Earth, but the Earth is at it's maximum tilt this time of year so the ecliptic plane, as projected on our sky, would intersect both the eastern and western horizons further north than at other times of the year, right? If that's correct then bodies traveling along or near the ecliptic would be both rising and setting the furthest north of the year (certainly our sun, which travels along the ecliptic does this, no?).

If the moon is at most only 5 degrees off the ecliptic, I just can't visualize the moon rising the furthest south of the year during the summer solstice no matter what it's phase. I must be missing something... :(