BINOCULARS & TELESCOPES

First, I suggest that before you buy a telescope, use binoculars to look up at the sky. The reason for using binoculars instead of a telescope is because a binocular is really two small telescopes that allows any amateur to examine the sky. An amateur astronomer should use a good pair of binoculars to develop the skills of locating objects in the sky. Most importantly, a good pair of binoculars is cheaper than a large telescope. It can be stored easily and if your interest in Astronomy wanes, you'll be left with a good pair of binoculars for any type of use. Binoculars also allow the viewer a wider scope of the sky and are also good for relaxed viewing.

Before you go out to buy a binocular, you have to understand the technical facts first. The numbers commonly seen on binoculars include 7 x 35, 7 x 50, 10 x 50, etc. The first number represents magnification which is important for determining the type of viewing you want to use with the binocular. The last number is the size of the objective lens (the piece of glass opposite the eyepiece) which is important for the power of light-gathering. A binocular with a magnification of 10 will magnify an object 10 times greater than your eye actually does. The larger the objective, the more light it can gather. For example, a 7 x 20 binocular magnifies an object seven times greater and can gather light with a 20mm objective lens. A 7 x 35 will also magnify seven times greater but will allow a fainter object to be seen. So if you want to see faint stars, it is recommended that you purchase a binocular with a larger objective lens. A larger magnification actually makes the field of view smaller so it could better view a distinct object instead of an entire grouping.

Binoculars can be so large they require mounts to steady them but these are better for astronomers who already know what they are doing and can spend more money on them. For starters, we recommend a general purpose binocular that can be used for viewing the sky but also for looking at birds or other varied uses. For example, I used a very small 8 x 21 binocular that has a range of over 1000 meters. It is of high quality optics which can mean the difference between a good binocular and a bad one. With this small binocular, I could see distinct features on the moon and when the comet Hale-Bopp passed by, I saw it in a much greater detail and I didn't need to use a telescope. With binoculars, you could see the planets (except for Pluto), stars, constellations, the moon, and the sun. It is best to use a mount to stabilize the binocular for easy viewing.

Even though a pair of binoculars offers an amazing view of the solar system, a telescope would offer a much more detailed look into the universe. However, do not just go out to any store and buy a telescope without knowing what to look for and how they work. There are several types of telescopes available for astronomers to buy and are categorized as either reflector or refractor.

A Newtonian reflector uses a paraboloid mirror to reflect the image to the eye. A reflector is cheaper than a refractor telescope because they are easier to build, thus cheaper to produce. However, because it is cheaply produced, you must be careful how you choose a reflector telescope. Due to poorly shaped mirrors and optics, spherical aberration occurs. A spherical aberration occurs when the shape of the mirror causes light to reflect to a different focus. An image would look sharper at one point while the rest of the image is fuzzy. A reflector works by light reflecting light from larger primary mirror to a second diagonal mirror which reflects the light to the viewer's eyes. About 15 to 35 percent of the light is lost this way. There is also another type of reflector called the Cassegrain. Cassegrain reflectors have a secondary convex mirror which reflects the light back into a hole that is specially made in the primary mirror. This allows a for shorter and smaller telescope.

A refractor telescope consists of a simple lens system with an object lens that gathers light and another lens system in the eyepiece that brings it to focus. The eyepiece is very important in determining the quality of the telescope because it controls the magnification. The refractor uses an achromatic lens to prevent chromatic aberration which causes light of different wavelengths to focus at different points. Refractor telescopes are good because they are easy to maintain and are best for viewing the moon and planets. A refractor allows the best view for bright objects in the sky because of their focal ratios. However, a refractor costs more money than reflectors and are not good for viewing dim objects. The cost of producing the lens is the primary factor in the high price of refractors but in our opinion, it is definitely worth the money.

A telescope is very similar to a binocular and the same method of magnification to the diameter of the object lens is used for the telescope. As before, it is recommended that you choose a telescope with an object lens with a wide diameter. It is better if the diameter of the lens is over 50mm because it allows for better light gathering.

Finally, when buying a telescope, make sure it comes with a very sturdy mount. The telescope could be of the finest optics but without a good mount, it would become useless since a steady image cannot be formed. In our opinion, the altazimuth mount is the most suitable. This mount is cheap, easily constructed, and fairly stable. Most telescopes are used with altazimuth mounts. However, cheap and long altazimuth mounts are very unstable. It is recommended that you look for an altazimuth mount with wide legs that offer better support. The heavier, the mount the better.

Here is what we recommend for starters who have never used a telescope before: A reflector telescope (Since it is cheaper) with a focal ratio of f/8 and an objective lens of 80mm. The 50mm lens is very common but the light gathering power is severely limited at 50mm. Also, it is important that the optics in the telescope are not poorly made. Anyone who is considering buying a telescope should first look at the magazine SKY & TELESCOPE.