 There are a few instruments that can immerse you in the beauty and wonder of our universe quite like a telescope. And we've been using them for over 400 years to expand our cosmic horizons. And if you have the right one in your backyard, it can expand yours as well. This is your space pod for April 24th, 2015. In order to get a clear picture as to what telescope you should get yourself, you first have to understand some fundamentals about telescopes. Now, we won't be covering what telescope you should buy yourself. That'll be coming in a later space pod. First off, there are three distinct types of telescopes. Refractors, Reflectors, and Cata-Dioptric Telescopes. Refractors use lenses. Reflectors use mirrors. Cata-Dioptric telescopes use a combination of lenses and mirrors. For the sake of simplicity, we'll start off by looking at refractors and reflectors. Whenever you ask someone to draw a telescope, the design they'll most likely whip up is a refracting telescope. These telescopes use convex lenses to magnify the image. With a refractor, the light travels from the opening of the telescope straight down and into your eyes. This allows them to produce exceptionally sharp images. One of the downsides is that there's a limit to the size of a lens in a refractor. Glass is extremely heavy, and the larger the lens, the heavier the telescope will be. From 1610 to the middle of the 1700s, the refractor telescope was the standard for astronomical study. Now, if you'd like something a little bit more modern, the reflecting telescope is probably going to be your choice. The principal difference is that in a reflector, a mirror is used to gather light. The design for reflectors was originally drafted up in the 11th century, but no serious attempts were made to build one until Isaac Newton did so in 1668. But due to poor manufacturing techniques, it wasn't until the 18th century when reflectors rose to prominence. Because a mirror does not need to be set to a certain thickness like a lens does, you can actually make massive mirrors that are extremely lightweight. And the bigger your mirror, the more light you can collect. And the more light you can collect, the thinner an object you can see. That's why today almost all of the major research telescopes on earth, from the Keck Observatory in Hawaii, to the very large telescope in the Atacama Desert in Chile, and even the Hubble Space Telescope, orbiting 550 kilometers above us, is a reflecting telescope. With hundreds of years of heritage, tinkering, and perfection, refractor and reflecting telescopes are exceptional works of scientific endeavor that let you see a bit further than you would on your own. Thanks for watching this Spacepod. I'm Jared Head. Don't forget to comment on social media, subscribe to us, and we do have a Patreon campaign. You can actually find it for just the Spacepods at www.patreon.com. So an immense thank you to all of you who have already started contributing to this great addition to tomorrow. So until the next Spacepod, keep exploring.