Backyard Astronomy - Gazing Into The Past

Astronomy continues to be one of the more popular hobbies. One of the major reasons is because you can stargaze just about anywhere. Although country settings away from city lights are best, everyone can see the moon. And even though the closest star (after our sun), Alpha Centauri is over 4 light years away, can be seen easily with the naked eye.

While simple stargazing with the naked eye is great fun, using a telescope can be awe inspiring. The view of the heavens through even a small telescope is something that has to be experienced to be appreciated. Even though modern technology allows us to view the celestial realm with images on tv and through the internet, there is nothing quite like seeing it though a telescope.

Different Telescopes

There are basically three kinds of telescope. The refractor and reflector and catadioptric. The refractor telescope collects and bends light with a convex lense and eyepiece. This bending or refracting concentrates the light rays to a small focal point making things appear larger or brighter. The reflector telescope on the other hand, as its name suggests, reflects light from a convex mirror in the back of the telescope to another mirror in the front and finally to the eyepiece. The convex shape of the mirrors "scoop up" and concentrate the light to a focal point thereby magnifying an object. Caution: Objects in a telescope appear closer than they really are!

The third type, called Catadioptric, combines features from both reflecting and refracting telescopes.

Which one is best? For image quality and portability, my choice is the catadioptric. It's easily transported and has the best features of both the reflector and refractor telescopes. Because of the design, catadioptric telescopes are almost completely free of the coma found in reflectors and the chromatic aberration in refractors. Chromatic aberration is the distortion of color due to a lenses inability to bring various colors in the light into focus. Coma is the distortion of an object at the edge of your field of view.

Convenience is another factor to consider. If you have to transport your telescope as I do you'll appreciate the catadioptric's compact size, light weight and how easy it is to set up and take down.

Travel Through Time

We all know light travels at an unimaginable speed of 186,000 miles per second. Even our sun's light takes about 8 minutes to reach us once it's left the surface. Now think about our closest neighbor, Alpha Centauri. It's over 4 light years away so the light from its' surface began its' journey over 4 years ago. We are actually seeing it as it was more than 4 years in the past. In a very real sense we are looking back in time. Think back to what you were doing 4 years ago. Whatever it was, while you were doing it, light emanated from the surface of Alpha Centauri and came screaming along at 186,000 miles per second on the long journey toward earth, arriving here just a few minutes ago. Alpha Centauri is actually part of a star system. 3 separate stars, Alpha Centauri A and B form a binary while Alpha Centauri C is 13,000 Astronomical Units (AU) away. This is part of the reason it's easily seen with the naked eye, you are actually looking at 3 stars instead of 1.

Closer To Home

One need not look outside our own solar system to find amazing sites in the night sky. The moon may look smooth when seen with the naked eye but train a telescope on it and prepared to be wowed. The level of detail will depend on your telescope but the craters and jagged mountains are clearly visible. The best viewing, in my opinion is when the moon is in a crescent stage as the shadow created by the earth allows for much more detail to be seen. I saw the moon for the first time through a telescope years ago. I watched as it slowly drifted past my field of view and could almost feel its' movement. Of course I knew it moved along its' orbit around the earth but to actually see it moving was an incredible experience.

Saturn, probably the most fun to observe because of the rings, makes for spectacular stargazing. Depending on the time of year, the rings of Saturn are visible and to this observer, quite breathtaking. While I couldn't discern any colors or variations in the rings, they appear quite distinctly from the planet itself, something I'd seen only in books prior to that.

Stand on the shores of any ocean on earth and get a sense of the sheer enormity of it. Then realize that it's not even a drop in a bucket by comparison to the size of the sky it sits beneath. Looking up at the stars at night makes you realize just how massive everything really is. There is no number that can truly measure or even estimate its' size or dimensions. The only thing that can even remotely compare to the wonder of space is the imagination of those who view it.

The Enchantment of Optical Telescopes

People have long looked to the stars for answers to numerous questions. What exists beyond planet Earth? Are humans the only intelligent life in the universe? What do other planets look like? In order to answer these questions and many more, craftsmen and scientists built and perfected telescopes made to search the heavens for answers. Different types of optical telescopes were invented over time to help mankind search the heavens.

Galileo is credited with perfecting the first optical telescope used in astronomical exploration, improving on the design of spectacle-makers and opticians. The Galilean telescope is classified as a refractor, the earliest and simplest optical telescope type created. Refractors work by bending light when it passes through a lens set at the front of a long tube. All light rays meet at the back of the tube, converging on the eye of the viewer. These telescopes are cheaper than the other types and are simpler to make than later varieties of telescope.

Refractors, however, had several flaws, one of which is the distortion--called chromatic aberration--that occurs when lights of different wavelengths come to focus in different places within the tube. Isaac Newton solved this problem by inserting mirrors in the telescopic tube, inventing the reflector telescope. Some of these mirrors decrease the amount of light that enters the telescope, but the increase in clarity is outweighs the decrease in light. These telescopes are good for beginners and experts alike and are used in numerous small and large-scale astronomical explorations.

Reflectors enable the construction of large telescopes with sizable reflectors built in them. Scientists learned that they could get better results with a large collection of smaller mirrors than they could with a small number of larger mirrors. These large telescopes have taken clear pictures that have astonished scientists and the general public with their content. Size and number of mirrors, however, are not the only factors involved with the clarity of telescopic photographs.

The Space Age presented astronomers with opportunities never before open to them. In 1990, NASA launched the Hubble Space Telescope into orbit, the world's first space-based telescope. Images obtained from outside the Earth's atmosphere are clearer than those captured beneath it because the atmosphere is constantly moving and shifting. This movement causes blurring referred to as "seeing," but this blurring is not present in Hubble photographs due to it being beyond the Earth's atmosphere. The Hubble will be replaced by the newer, more modern James Webb Space Telescope that will have enhanced visual and infrared viewing capabilities.

Other types of telescope are the catadioptric and infrared telescopes. The catadioptric telescope makes use of both reflection and refraction to capture images and is generally contained in a more compact design than is often used for other telescopes. The Schmidt-Cassegrain model is the most popular catadioptric telescope and is quite popular with astronomers due to its image quality. Infrared telescopes see limited use because they are only effective in chilled regions and areas shielded from heat. They are used to detect emitted radiation in the electromagnetic spectrum and come in ground-based, air-borne, and space models.