what are the two main types of telescopes?what is the key difference between them?

There are two basic types of telescopes: refractors and reflectors. Both have their advantages. Properly outfitted, either will show you distant galaxies, the rings of Saturn, or the craters of the Moon.

Refracting telescopes gather light with a lens, directing it to the eyepiece. Small starter scopes are often of this type, as they are simple to operate and maintain. Larger refractors, however, become very expensive and are typically bought by avid enthusiasts.

Reflecting telescopes gather light with a mirror, reflecting it before directing it to the eyepiece. Reflectors typically give you a wider aperture for the dollar. They require more care and maintenance, however. The simplest type of reflecting telescope is called a "Newtonian," after Sir Isaac Newton who invented them. When a Newtonian telescope in it's simplest and most user-friendly form, it's called a Dobsonian telescope after John Dobson who showed the world that you don't have to be rich to make your own telescope.

Hair Metal and Glam Metal are the same thing as Poodle Rock. PLEASE do not ever confuse this garbage with the glam rock/glitter rock scene from the early 70's which was a great, great thing. Speed Metal or Thrash Metal. Would'nt know. Sound the same to me. Death Metal and Black Metal. I MIGHT have this *** backwards (I kinda just got up) but one is your basic sntan obsessed metal and the other is a much more extreme form of it (and a much faster form of it). I think (here's where I might have it @ss backwards) bands like Venom, Bathory, Slayer etc would be Black Metal and bands like Mayhem, Abruptum, Satyricon, Taake, Emperor etc would be Death Metal. Hard Rock and Heavy Metal. Well back in the day stuff like Black Sabbath, Led Zeppelin, Uriah Heep, Deep Purple and the like were considered Heavy Metal and bands like Free, Humble Pie, David Bowie's Man Who Sold The World, Grand Funk Railroad etc were considered Hard Rock. It really was en extremely fine distinction, especially if you listen to any of these bands 35+ years later. But at the time a lot of "hard rock" fans would look down their noses at "heavy metal" fans and a lot the heavy metal fans would think the hard rock fans were pvssies. What makes it even wierder is that many of the bands that got categorised as "hard rock" were actually at time a LOT "heavier" than the bands being called "heavy metal"!

Focal points: Prime, Newtonian, Coude and......I forgot the last one