Video: Telescope Buying Guide: Refracting Telescopes

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A refracting telescope is the most common kind of telescope. Discover the difference between refracting and reflecting telescopes in this free video on home astronomy from a telescope salesperson.

- Telescope Buying Guide: What to Avoid

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Video Transcript

In this segment we will talk to you about refracting telescopes. These are telescopes that gather light through convex glass bringing it to focus down here with the eyepiece. Now a refracting telescope is typically what most people visualize when you say the word telescope. The traditional long tube, the eye piece here at the back is very simple and easy to use and typically pretty low maintenance. Scopes, refracting style are idea for lunar and planetary observing and at different price points can offer obviously different quality of the picture that you see. One of the advantages of a refractor is that they are relatively inexpensive from a beginner's point of view and if you are going to do terrestrial or day time viewing, you must have a refractor. Also for light polluted areas, areas like if you are in the middle of a city you want to gather some light but as you gather more light you gather light pollution as well so inside the city someone is viewing off a balcony or something like that. I will recommend usually an 80 millimeter refractor and realistically from there you will do lunar, you'll do planetary, you can do some double stars but basically where the refractors lack is just light gathering ability. If you want to see the more distant objects, if you want to get outside the milky way galaxy you really need to step up to more of a light bucket. I say refractors are relatively inexpensive to get started with but it also depends on the type of glass you are going to get into. Typically there are three types of refractors. There is what they call an acromat and there is an e.d. glass and an apo chromatic. Now with an acromat they are referring to how those colors, how the light path comes into focus to your eye. The red green and the blue light spectrum travel at different lengths so in an acromatic telescope all those colors don't quite hit your eye at the same point. That means as you are you are trying to push the magnification a bit you are going to get what they call false color or chromatic aberration meaning a bright object like the moon at 100 magnification might give you a little green or yellow or even purple hue to it that can be distracting for people that want to view planetary at higher powers. If you step up to what they call an e.d. lens, an extra low light dispersing lens that corrects that color a bit more for you so you can get higher magnification. Also the contrast gets a little darker too so that bright object stands out a little bit more. Refracting telescopes that boast that they are apo chromatic are truly the most premium instruments on the planet and they'll command a premium price as well. A guy like this right here will push the doz limits. When I said you can get 50 X magnification per inch of aperture right here, this little four inch scope because of its quality, because of the glass, because of the design can actually push 150, 200, 250 magnification without any false color. They have taken the time to make sure that the red, the blue, and the green hit your eye at the same time so an apo chromatic scope will give you no false color as you increase the magnification. There are exceptions of course but if you are looking at refractories you should understand the term acromat, e.d., and apo chromatic. This will help you in choosing a refracting telescope. Again the apo is the most premium instruments, the darkest contrast makes those dim fuzzies pop out a little bit better. As premium of an instrument as they are they still lack a little bit of aperture and we are going to talk about large Newtonian telescopes coming up.

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Telescope Buying Guide: Refracting Telescopes

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