Under what circumstances can one find the Sun on the ecliptic?
817446
The ecliptic is defined as the path thourgh the sky where the sun appears over the course of the year.  Thus, no matter when you see the sun it is on the ecliptic.  On the equinoxes the ecliptic and the equator of the earth line up, and on those two days you can find the sun on the equator, but the sun is always on the ecliptic.
712687
If you imagine a solar system that includes the sun and the Earth,and no other bodies, the Earth would travel about the sun in an ellipse (strictly speaking, the Earth and the sun would travel around their common center of gravity in ellipses).  An ellipse has two foci, which are points that define the ellipse in the same way that a point defines the center location of a circle.  Because the sun is so large and the orbit is so nearly circular, both of the foci lie near the center of the sun  So it is not correct to say that one of the foci is the sun -- both foci are in the sun, but they're really just mathematical points that define the shape of the orbit.\n\nWhen you add more planets to the mix, things get much more complicated, but one can think of each approximately elliptical orbit separately, and then there is a different set of foci for each pair of bodies if one neglects the influence of the other bodies.
1035386
Astronomers generally use either the equatorial or ecliptical reference frames. The standard reference plane for the equatorial reference frame is the earth's equator. The standard reference plane for the ecliptical reference frame is the plane of the earth's orbit around the Sun. The intersection of these two planes is a line that points in one direction towards the vernal equinox, and in the other direction towards the autumal equinox.\n\nIn both systems, the zero point of longitude (for ecliptic) or Right Ascension (for equatorial) is defined as the direction of the vernal equinox, also called the First point of Aries.
440880
Well I am not sure if it is proper to apply the term to the sun, but the sun's apparent motion against the background of fixed stars is always in the same direction as that of planets that are moving in the prograde direction.
749447
Hi. A good one might be Regulus because it lies pretty close to the ecliptic and is very bright. But you can use any star. For much better accuracy scientists use quasars due to their vast distance. This eliminates parallax error.
597835
It isn't "chance" although that is why it is the right/size to produce solar eclipses.\n\nThe moon is not perfectly symmetrical. The crust is thinner on our side, and the core (heavy part of the moon) is displaced towards our side. That acts almost like a handle for the earth's gravity. It has slowed to the point where the earth's gravity now keeps this side pointed towards the earth.\n\nHowever it is not perfect. As seen from the earth, the moon wobbles slightly --- both side to side and up and down. The motion is called libration and allows us to see more than half of the moon. We had a discussion on the yahoo lunar group recently with a link to an animated gif that showed the moon's libration.\n\nIf you are interested in the moon, try\nhttp://groups.yahoo.com/group/lunar-observing/\n\nChuck
1008903
yes, the sun is a good example
941426
Since the orbital plane of the moon is not the same as the ecliptic, and due to the eath axis or rotation being angled 23 degree, there will be variations as to how far North or South the moon will rise.  But this variation occurs over the course of a year, juts like the seasons.  If you mean "before" like a couple of years ago, then the answer is no.
630789
i want to see the daily path of the sun on the sky:\n\nrising from east and setting to west as everywhere on earth but going through north at noon not south as in northern hemisphere. must be fascinating to see: all shadows at noon pointing south instead of north\n\nlove your beaches too
1132045
A special case of annual aberration is the nearly constant deflection of the Sun from its true position by κ towards the west (as viewed from Earth), opposite to the apparent motion of the Sun along the ecliptic. This constant deflection is often erroneously explained as due to the motion of the Earth during the 8.3 minutes that it takes light to travel from the Sun to Earth. The latter is a type of parallax, and actually causes the apparent motion of the Sun along the ecliptic towards the east relative to the fixed stars. (8.316746 minutes divided by one sidereal year (365.25636 days) is 20".49265, very close to κ, but of opposite sign, east vs. west.) Nor is this the Sun's light-time correction because the Sun is almost motionless, moving around the barycenter (center of mass) of the solar system by usually much less than 0".03 (as viewed from Earth) during 8.3 minutes.\n\nAberration can be resolved into an east-west and north-south component on the celestial sphere, which therefore produce an apparent displacement of a star's right ascension and declination, respectively. The former is larger (except at the ecliptic poles), but the latter was the first to be detected. This is because very accurate clocks are needed to measure such a small variation in right ascension, but a transit telescope calibrated with a plumb line can detect very small changes in declination.
628171
The zodiacal light.  A faint glow from light scattered off of interplanetary dust along the plane of the ecliptic.  It lies along the ecliptic and is caused by reflected sunlight.
874513
If you are in the Northern Hemisphere and it is clear out you can use the big dipper to find the North Star (off the outside of the "cup").  If you are in the southern Hemisphere I believe you can use the Southern Cross similarly (points north south).\n\nIf it is near sunrise or sunset and you know roughly what lattitude you are at and what season it is you can get a rought idea of East or West and therefore North and South (for instance if you face West, north is to your right).\n\nObviously if you have GPS or a compass that makes all this much easier (assuming your compass is lit ;) ).\n\nIf it is very clear out you can probably see the Milky Way, and the galactic plane runs roughly North South.\n\nIf you are familar with the night sky and know what time of year it is you could get a rough idea of your lattitude and maybe longitude, and, even if you can't find the North Star or Southern Cross you could find planets and the orbital plane or a familar constallation and figure out the directions.\n\nRealistically if I didn't know where I was I would either go towards light if there was a bright part of the sky (city) or find a creek and fallow it since even if it is dried up, it is likely that it will lead you to a settled area or road and hopefully would have more shade from bushes and more food and water.
275393
The equinox is not a sudden event that flicks a switch or something, it's just the name we give to the instant when the equator is hit with direct sunlight.  It's simply a moment in a gradual cycle.\n\nEquinoxes: sun is directly over equator\nSummer Solstice (North): sun is directly over Tropic of Cancer\nWinter Solstice (North): sun is directly over Tropic of Capricorn
543648
Oh no, you've figured out my hoax!!! You busted me, you're right, its not round. Sorry, I get silly sometimes. If you are at a position when the moon passes directly perpendicular to you relative to the sun's position then you will see a perfect half lit moon. you can simulate this with a big right triangle by taking a golf ball or some other ball and placing it at the  90 degree corner and placing a flashlight at one of the other corners pointing directly at the ball. Now line up your sight from the third corner and you should see a perfect half lit ball. :)
1099920
I'd bet you can find it on this site:\n\nhttp://mathworld.wolfram.com/Ellipse.html
796172
Equinox means equal night......the two days a year ( March and September) when the sun at noon is directly overhead at the Equator. The two solstices are Summer when the sun is directly overhead at 23N and the Winter when its directly overhead at 23S...so your shadow would point south everyday of the year at 23S except on the Winter Solstice when there would be, in theory, no shadow at all since the sun is 90 degrees overhead
184588
we know the shape of the solar system because we know from tracking the movement of planets that they orbit the sun, as they orbit the sun they must be going round it, so that is a slightly stretched oval shape. We can estimate where planets are (i.e. how far away they are) by using stars that we know are different distances away and measuring or by using the Hubble Telescope that can see all the way to Pluto and further and measure the distance.