Transit : when a star crosses the observer’s meridian a.k.a. culminate. Vertical circle. any great circle passing through both the observer’s zenith and nadir. It receives its name from the fact that they are perpendicular to the horizon.

Since stars change their position with respect to your horizon throughout the night, their altitude-azimuth position changes. This system is fixed with respect to the stars so, unlike the altitude-azimuth system, a star’s position does not depend on the observer’s location or time.

When is a star highest in the sky? Looking at the diagram on the right, it is clear that a star reaches its highest point in the sky when it crosses the observer’s meridian, the line which passes through the zenith and the south point on the horizon.

Meridian Passing: The three columns on the right all refer to the instant when the Moon passes the meridian (longitude) of the selected location. It indicates how far up the Moon appears in the sky. At 0 degrees, the Moon’s center is on the horizon, at 90 degrees, it is in the zenith position directly overhead.

From Earth’s North and South Poles, all the stars appear as circumpolar. Meanwhile, at the equator, no star is circumpolar.

So at any hour of the night, at any time of the year in the Northern Hemisphere, you can readily find Polaris and it is always found in a due northerly direction. If you were at the North Pole, the North Star would be directly overhead. That’s true now, anyway.

Magnes

Yup, there really is a magnet found in nature! Lodestone, a naturally magnetized piece of magnetite, attracts iron, so it is technically a magnet. There are some fun stories about the ancient discoveries and uses of magnetite and lodestone on our blog.

Q: Are bigger magnets stronger than smaller ones? A: Generally yes, but not always. A larger magnet made from the same material and shaped in the same way as a smaller one will be stronger.