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On Tue, 13 Jul 1999 you wrote:
> Hi,
> I'm working on a children's book about the moon. I would like to know
> if the moonrise position on the horizon stays basically the same all year. I
> thought I came across the fact that the moon rises in the same place once
> every 50 something years. Therefore it takes along time to make a complete
> circle around the horizon. If someone (eg a child) were watching the moonrise
> each night, they would not notice much -if any- difference in where it rose.
I am not certain exactly what source mentioned this, but I would doubt
its authenticity. (It also depends what the source means by rising in
"exactly" the same spot.) The moon completes one complete circuit through
the sky every 28 days. The moon's orbit itself changes in a regular
fashion, completing a cycle every 18 years. If someone were to watch the
moonrise each night and make a careful note about where it rose (i.e. what
house or tree it rose over, or what stars the moon was close to in the
sky), the changes from one night to the next would be noticeable.
> Also, the moon rises about an hour later each night. Is there a chart
> that could tell me when the moon rises for the month of July and August? I
> think we'll be able to see the new moon tonight, and I'd like to be on the
> lookout for it for the next 30 days. I'm guessing it will rise about an hour
> after sundown tonight- about 9 pm or so.
The Lick Observatory outside of San Jose has observing calenders, which
include the moon rise and moon set times, at
http://www.ucolick.org/~npm/Cal2K/Lick/lick1999.12
The times are in 24 hour time. For other points on the Earth, the moon
rise and set times can vary by up to an hour in each direction. This is
again due to the Earth's shape. The exact rise and set times at your
location can be calculated, but it is rather complex.
> May I email more questions later? I'll be wondering about the shape
> of the moon in different parts of the world. (I know in Australia, the moon's
> shape is opposite ours in that a new moon has the shape of our old moon.)
In the southern hemisphere, the moon appears to go through its cycle of
phases "backwards" as compared to what we are used to in the Northern
Hemisphere. This is due to the Earth's roundness. Other than that,
however, the moon's phase looks identical everywhere in the world at the
same instant.
Feel free to email more questions at any time.
Sincerely,
Kurtis Williams
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