Posted by Caer on October 20, 1997 at 09:31:02:
In Reply to: I still don't get these questions: posted by Isaac Chang on October 19, 1997 at 18:48:12:
I can give you some hints ....
: 1. At what location on Earth is the north clestial pole
seen on the horizon?
Take a tennis ball. With a marker, put a dot on the
north pole (top of the ball)and one on the south pole
(bottom of the ball). draw a line around the middle
of the ball - that's the equator.
Hold the ball straight up so that N is up.
Remember that if you're at the north pole the
north celestial pole is straight above you. Remember that
on earth you can only ever see one hemisphere at a time,
so at the north pole you can only see the northern
celestial hemisphere. Now move the north pole dot so that
its on your horizon - at the edge of the north celstial
sphere. Now which part of the ball is straight up?
: 2. Where do you have to be on Earth in order to
see the Sun at zenith? If you stay at one such location
for a full year, on how many days will the Sun pass through
the Zenith?
ok, where on earth does the sun shine the most? Where
is it warmest? Remember that the celestial equator and
the earths equator are just a continuation on each other.
Remember that the eclitpic, the line that the sun follows
in the sky, crosses the celestial equator at two points -
the vernal equinox and the autumnal equinox.
: 3. Where do you have to be on Earth in order to see
the south celestial pole directly overhead? What is the
maximum possible elvation of the Sun above the horizon
at that location? On what date is this maximum elevation
achieved?
Where do you have to be on Earth to see the north
celestial pole overhead? (see ans to q1.) So equally,
where do you have to be to see the south celestial
pole overhead? Look at fig 1-15 on page 22 to figure out the
rest of the question.
: 4. What is the phase of the moon of it a) rises at 3am b) sets at 9pm? At what time does c) the full Moon set? d) the first quarter Moon set?
The diagram on page 25 should help you here. If you got a
handout from my discussion sections the diagram on
the back of that should help too.
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