How to Buy Your First Telescope

Many people think that a telescope is mainly used for magnification: making the stars bigger. The bigger the stars are in your view the easier it is to see them, right? This makes plenty of common sense, however magnification is not the most important thing in choosing a telescope. Many cheap telescopes will boast 500x magnification and you might think you are getting a good deal, but often times it is very difficult to see anything with these telescopes.

The most important job of a telescope is to intensify light in the image you are viewing. Magnification is important but if there is not enough light in the image you will not be able to adequately make out details, no matter how big they are. A 50x magnified image with plenty of light is far better than a 500x magnified image that is dark and indistinct.

A very important term to understand when going to buy your first telescope is aperture. This is the size of the opening of the telescopic lens, which determines how much light enters and thus how sharp and clear the image will be. For the most part the wider the aperture the better the telescope.

Aperture is not the only determinant in quality of telescope, though. There are two basic forms that telescopes take; each of them brightens images in their own way, increasing or decreasing quality.

Refracting Telescopes

Refracting telescopes provide the best and sharpest images in terms of quality to aperture ratio. A refracting telescope consists of a long tube with the objective lens (where light enters) at one end followed by a long, narrowing tube. The tube narrows from the aperture to the end of the telescope where the eyepiece lies. For most people this is what we first think of when we think of a telescope.

The refraction takes place as light is passed through the narrowing tube. This narrowing focuses the image, making it sharper and more clear.

Reflecting Telescopes

Unlike refracting telescopes, reflecting telescopes remain the same length from one end of the telescope to the other. The reflecting telescope does not have an objective lens, rather light enters the tube, travels all the way through the tube and hits what is known as the objective mirror. The light bounces back to the front end of the tube where there is a second mirror, which then bounces the image back to the eyepiece.

These mirrors which reflect the image first one way then the other are why we call these reflecting telescopes. A reflecting telescope, compared to a refracting telescope of similar aperture is not going to produce as high quality of an image.

You may also see reflecting telescopes referred to as Newtonian telescopes, named after famed scientist Isaac Newton.

Catadiotropic Telescopes

One third type of telescope to mention is the catadiotropic telescope. This is essentially the same as a reflecting telescope but has a correcting lens placed in prior to hitting the objective mirror: this gives extra sharpening of the image and allows for greater aperture in a telescope with a shorter tube, making for an overall smaller telescope.

Which Telescope is Right for You?

If you are looking to buy your first telescope, you are definitely going to want the most bang for your buck. Generally speaking the best rule of thumb is that the bigger the aperture, the better image you are going to get with the telescope.

Telescopes often run in the $100 to $150 range, however if you are serious about buying a decent telescope you are probably going to want to look for something more in the $300+ range. Oftentimes cheaper telescopes over-emphasize magnification while providing little aperture, leading to dark and blurry images.

The best rule of thumb, though, is simply to find the telescope with the largest aperture that you can afford. Take a look around at telescopes available, and see what they have to offer. Refracting telescopes will provide images with a bit more quality, however do to the nature of their working they are often limited in size if you are looking for something a bit bigger.

Mounts and Eyepieces

The last thing to consider when purchasing your first telescope is the mount and eyepieces. An eyepiece is an essential part of the telescope, and every telescope comes with at least one (sometimes several). This is primarily where magnification of the image takes place. Although magnification is the primary function of the eyepiece; for example some eyepieces also allow for wider images (allowing you to see more).

Mounts are not technically required in order to use a telescope, however holding a telescope by hand means a) the telescope can't be very large and b) few people can hold a telescope nearly steady enough to keep their focus on an object in the sky, where the slightest movement can often mean completely losing track of what you were looking at.

The most basic mount is a simple tripod mount. Many telescopes come with a tripod built in, however for more expensive telescopes you will sometimes find that you will need to purchase the mount separately. Mounts come in two basic types: altazimuth and equatorial. This refers to how you can move the mounted telescope, either in relation to the horizon (altazimuth) or the celestial equator (equatorial). Mounts are typically moved by hand but some can also be motorized, allowing for automatic tracking and movement.

Once you've got your telescope, you're ready to start the fun of exploring the stars. There is a whole universe out there to explore and with the right equipment is all yours for the viewing.