Refractor, or dioptric, telescopes are the oldest existing model of telescope. They were used by Galileo and Kepler, among other notable astronomers. Though their design has been improved over the centuries, the general technology has remained the same. Now it is possible for anyone to own a small version of this powerful tool. But, with other choices of telescope available today, how are you to know if the refractor telescope is going to meet your stargazing needs? Let's find out.
How They Work
Refractor telescopes use a combination of a curved lens and an eyepiece to project an image to you, the viewer. The lens works as an objective, catching a large amount of light and focusing it into a much smaller beam. The beam is directed into the eyepiece, which you can then use to adjust the focus and attain clarity. Often the eyepiece will be set at a 90 degree angle, functioning with the aid of a mirror. This allows the device to be used more comfortably.
The only major alternative to the refractor telescope is the reflector telescope, which uses a series of mirrors instead of a lens to capture light. The reflector telescope was invented to give stargazers another option in the 16th century, at a time when the lenses in refractors tended to have manufacturing flaws. Since production methods have changed since then, the flaws apparent in the refractor model have diminished The choice is really up to you. However, the two models of telescope have different strong points, so there are a few things you will want to consider.
If you're looking for a small telescope, the refractor model is slightly cheaper. A good starter size is about 60mm, and that can run you €50-70 (that's $70-100 American). If you're looking for something bigger, it is important to understand that lenses get expensive to make as they get larger and mirrors comparatively do not. At larger sizes, a refractor telescope can cost significantly more than a similar reflector, so keep that in mind. If you're a beginner and you're keeping it small, stick with the refractor.
Sir Paul McCartney croons that Venus and Mars look alright tonight. If you want to see for yourself, the refractor telescope is your best bet. Refractors are more capable of focusing closer objects. The moon, the planets, even the sun (yes there are filters that allow you to view it, though staring at the sun through a magnifying lens is still never advisable) will come in clearer through this model. If you are trying to focus on dimmer, more distant objects like other galaxies and nebulas, then the refractor is not as effective and you might consider the alternative. However, to focus on something so distant you would have to consider a bigger scope anyway.
So, when should you use a refractor telescope? A refractor is recommended if you are a new stargazer. There are no real flaws to set it below the reflector model, and the smaller refractors are cheaper. It is useful for viewing most objects within our own solar system, and is comfortable to look through if it has an angled eyepiece.
Once you have purchased your new telescope, try to set it up outside on a clear night. Looking through a house window will never get you the best results. Also, if it is a particularly warm or cool night, give the instrument 20 minutes to adjust to the temperature before viewing. This will also improve your results. Finally, remember to have fun. The cosmos is an intriguing sight.