Astronomy

Many amateur astronomers who live in and around major cities enjoy wonderful views through their telescopes on any clear evening, but light pollution comes in two varieties: sky glow and local, or line-of-sight, glare. Sky glow refers to the orange glow we see rising above our horizons, the combined effect of hundreds, even thousands of lights on buildings, in parking lots, and along roadways all casting some of their light skyward. The net result extinguishes faint stars and washes out the sky. The best place to view the night sky is out of town where there are no lights from buidlings.

Which telescope?

A larger telescope will gather more starlight regardless of where it is located. A 12-inch telescope will show more stars than a 6-inch telescope.

Urban astronomers gain great advantage from using computerized telescope mounts. While star-hopping is a wonderful way for locating targets from a dark-sky site, it is difficult to do if the sky is so bright that reference stars are few and far between.

One of the most effective ways to improve the view is to add a tube extension in front of the telescope, this will block stray light. This is especially important with Newtonian reflectors, where the focuser is often so close to the front of the tube that side light can shine over the edge and right into the focuser. Extending the tube at least one diameter in front of the focuser will eliminate the problem and improve contrast noticeably. Be sure to paint the inside of the extension flat black.

What to look at

Halfway between the celestial poles is the celestial equator, a projection of Earth's equator onto the sky. The stars on the celestial equator rise due east and set due west. Delta Orionis, the northern-most star in Orion's Belt, lies almost directly on the celestial equator.

Early navigators learned to use the rising and setting stars to find their way. Stars were important to Pacific Islanders as they traveled from one island to the next. Surrounded by the Pacific's waters, there was no land to serve as a reference point. Over time, the observations and records of these star patterns provided a method for navigation that was passed on from one generation to the next.

In the Northern Hemisphere, the star Polaris (the North Star) lies very close to the North Celestial Pole and never rises or sets. Instead, Polaris traces a very small circle around the North Celestial Pole and is therefore circumpolar. Other stars, like the Big Dipper also circle around this "pole star," but they do so in much larger circles.

From more northerly latitudes, there are many more stars that never set. Whether or not a star is circumpolar depends on your latitude. For example, if you were standing on the North Pole, all the stars in your sky would be circumpolar. They would move horizontally, circling around the celestial pole overhead.

For latitudes between the North Pole and the equator, the North Celestial Pole is tilted away from your zenith, the point directly above you. In fact, the angle of Polaris above the horizon is approximately equal to your latitude.

What planets

Mercury

Mercury is the closest planet to the Sun. Its surface has many thousands of impact craters as a result of being bombarded by objects since the solar system's early days.

Venus

The surface of Venus is a very unpleasant place featuring very high temperatures, winds that blow hundreds of miles per hour and an atmosphere of sulfuric acid. Venus is an example of runaway greenhouse effect on a planetary scale.

Mars

It's distinctive rust color is easily seen through a small telescope. The surface of Mars features many mountains, canyons and even polar ice caps that look a lot like those here on Earth. In ancient times, Mars may have harbored some kind of life, and there is a lot of research going on now trying to get a definitive answer as to whether we are the only life forms in the solar system.

Jupiter

Jupiter is the largest planet in our solar system. It has at least sixty-one moons and features the Great Red Spot, which is a huge "storm" that has been observed from here on Earth for over three hundred years.

Saturn

Saturn is one of the most beautiful planets in the solar system. It's fascinating system of rings have been a source of wonder since we first saw them with the earliest telescopes. Although the rings look fairly simple through a small telescope, spacecraft pictures have revealed that what looks like two rings through a telescope is actually hundreds of individual ring systems. In addition, Saturn has so many moons that it is like a miniature solar system.

Uranus

Uranus is one of the giant gas planets in the solar system. Its mysterious blue-green color provides very few clues as to what is going on underneath the surface clouds. Uranus also has a very faint ring system that we didn't know existed until the planet was visited by the Voyager spacecraft.

Neptune

Neptune was the last stop the Voyager mission made before it left our solar system. What we found out from Voyager was that Neptune has winds that blow hundreds of miles per hour and a moon that features "geysers" of nitrogen that erupt and leave dark marks on the surface.

The Minor Planets of our Solar System

Pluto Pluto is one of the "dwarf planets" in our solar system. Pluto is so far away that the Sun is just a dim point of light that looks a lot like any other star. Pluto has three moons, one of which is almost as big as the planet itself.

Moon

The Moon is something that we are all used to seeing. It's also a very good place to start your program of becoming an amateur astronomer. As you no doubt already know, the Moon goes through phases on a cycle that lasts a little over twenty-eight days and is our nearest celestial object.