Friday, September 23, 2011

Factors to Consider When Buying A Telescope

When you first become interested in buying a telescope, it can be somewhat of a daunting task. What kind of telescope do you really need? There are so many different kinds to choose from and a very large price range too. What do you want your new telescope to do, and do you really need all of the bells and whistles available? You don't want to pay good money for a telescope that won't give you a satisfactory experience, but neither do you want to pay for features that are just not necessary for what you need.

Here are a number of tips to keep in mind when you are thinking of buying a telescope.

Type of Objective - There are basically 2 kinds of telescope objectives available for home use. These are:

1. Refractor telescopes - these telescopes use a series of lenses to focus light onto the eyepiece. These telescopes are very rugged because they are a closed system and there are no mirrors to adjust so there is virtually no maintenance involved. These models produce some of the sharpest images available, but can be much more expensive to get a really good one.

2. Reflector telescopes - these telescopes use a series of mirrors to focus light onto the eyepiece. These telescopes are usually much more economical, but they are an open tube, so dirt and dust can collect on the mirrors. The mirrors will also need to be periodically aligned as well. However, you can get the most for your money with one of these if you don't mind the maintenance.

Aperture Diameter - The telescope's main function is to gather light, therefore the diameter, or at least the proportion of the objective's aperture is very important. The telescope's light-gathering strength is proportional to the objective's surface area, so bigger is not necessarily better unless the proportions are correct. A good rule of thumb for aperture width is about 3 inches (8 cm) for Refractors, and 4 - 8 inches (10 - 20 cm) for Reflectors.

Eyepiece - One of the most important things to check out when buying a telescope is the eyepiece. If you can afford it, get an eyepiece that is adjustable so that you can adjust the magnification - or at least get a telescope that has interchangeable eyepieces. A good steady focuser is also very important as you don't want the telescope to shake while focusing.

Magnification - Most beginners think that the most important feature in a new telescope would be high magnification, but that is not always the case. If the telescope's light gathering ability is insufficient, all the magnification in the world won't help. A magnification of 40X to 60X per inch of aperture is usually sufficient. The ability of the scope to enlarge an image and keep it sharp mainly depends on the lenses used and the focal length of the telescope.

Mounting - Last but not least, consider how your telescope will be mounted. Will it be mounted rigidly or will it be a portable mount? Make sure whatever mount you get has a low center of gravity so it won't tip over, and that it is the right size for the telescope you get. Mounting it at the right height as to avoid back fatigue is also very important.