Hello and a Question

[animatix]

Hi,

I have always loved the night sky. Very fascinating. But I've always live in an urban area and had to travel a bit to really see the beauty of it.

I just moved to a new house in the country. Very nice night sky view (and I just won a telescope from the Canadian Cancer Sweepstakes! woohoo).

So, being a total neophyte, I have a question for someone more astronomically inclined than I.

Q: I have observed, during my several months here, that the moon does not rise from a predictable spot on the horizon each night. In an urban setting you can't see this, but here I have a clear view of the horizon. One night it rises directly across the lake between two, large, oak trees and the next it rises around - I'm guessing here - about 10 - 15 degrees to the NW of the previous position.

What is the cause of this?

[BMAONE23]

I would suppose that this is caused by the fact that the moon doesn't orbit the earth at the equater. It is inclined by a couple of degrees relative to the equater. So as the moon travels around its 29.4 day orbit, it shifts relative to the equitorial plane with 14.7 days above and 14.7 days below the plane of the equater. Then, much like the Sun's location in the sky changes with the seasons, (June it is north of the equater, December it is south of the equater) The same happens with the moon on a monthly basis.

[Chris Peterson]

Q: I have observed, during my several months here, that the moon does not rise from a predictable spot on the horizon each night. In an urban setting you can't see this, but here I have a clear view of the horizon. One night it rises directly across the lake between two, large, oak trees and the next it rises around - I'm guessing here - about 10 - 15 degrees to the NW of the previous position.

What is the cause of this?

It happens because the location where the ecliptic intersects the horizon changes over the course of each day. The Moon travels close to the ecliptic, and rises about an hour later each night. Because it is at a different time, the azimuth of the ecliptic is different each night. Over a month you'll see the azimuth of the moonrise sweep from north of east to south of east and back.

[animatix]

Thanks for the answer Chris.....makes perfect sense now...