How Do You Calculate Celestial Coordinates and Times in Astronomy?

[lightsilver]

Alright, so basically, I'm freaking over this. Not littiorally, because the assignment isn't worth THAT much. But I've been working on my astronomy assignment ALL DAY. And there's some questions I can't get. I can't seem to find the answers (with reasoning) anywhere. I've tried yahoo answers aswell, so far to no avail.

So I'll just copy/paste what I put at yahoo answers. Any help for anything is really helpful. For my class I'm using the textbook "Universe Eighth edition", by roger freedman or something. I REALLY appreciate any help from anyone on this, because it's due pretty early tomorrow.

"Alright, so basically I'm doing an introduction Astronomy course, and the TA is nowhere to be found. So I was hoping someone could help me with a few of the questions I can't quite figure out, how to figure out. Not nescessarly the answers, because it's more important I figure out -how- to do it.

2)In each of the following, give the azimuth and altitude of a star which is:
(c) at the intersection of the Celestial Equator and the Meridian at latitude 45º N.

--
3)
Suppose that you live at a latitude of 40º N. What is the altitude of the sun above the southern horizon at noon
(a) at the vernal equinox?
(b) at the winter solstice?

I think for this one, the answer is is 63.5ºN, and 26.5ºN, for a and b resepectivly. But I'm not sure. And I'm also not sure how to set up a drawing for it?

4)
a) What is the right ascension of a star which is on the meridian at midnight on September 23rd ? Explain
b)What is the sidereal time when the vernal equinox rises? Explain
c) On what date is the sidereal time closely equal to the solar time? Explain

for 4.c, I think the answer is the Sep. 21st, but I forget the word for it. I'm not entirely sure why however.

I don't need the answers to all of them either (well, I do), but any help is greatly appreciated.

Thanks"

 

[lippyka]

Answer to 2(c): The azimuth of the star would be 0°, and the altitude would be 45°. Answer to 3(a): At the vernal equinox, the sun's altitude above the southern horizon is 63.5°. Answer to 3(b): At the winter solstice, the sun's altitude above the southern horizon is 26.5°. Answer to 4(a): The right ascension of a star which is on the meridian at midnight on September 23rd is 0°. This is because on this date, the vernal equinox is in the 0° position in the sky, and thus any star which is on the meridian at this time would also have a right ascension of 0°. Answer to 4(b): The sidereal time when the vernal equinox rises is 0h. This is because the vernal equinox is in the 0° position in the sky, so at this time the sidereal time will be 0h. Answer to 4(c): The date when the sidereal time is closely equal to the solar time is September 21st. This is because the Equinoxes are the dates when the Sun moves from one zodiac sign into another. On this date, the Earth's rotation will be in perfect sync with the Sun's position in the sky, and thus the sidereal time and the solar time will be equal.