Optics 101: The Star Gazer Must Move On – Telescope Types

The historical background of the invention of and development of the telescope is more than adequate for me to take but little time to present it here other than to reference of course the inventor Hans Lipperly, and certainly the earliest developer Galileo Galilei. It must be stated here thought that arguments aside as to invention and development of this marvelous instrument, it is but one of many areas of science, and it is this science subject matter that must be considered at this point. There are so many science subjects important in our daily lives that do not necessarily make it to early classrooms as Astronomy does. What then gives the stars and star gazing a level of popularity that goes beyond the other sciences available in pre-college classrooms.
Well, as Stephen Colbert might say, “It’s time for truthiness.” But, for me it would have to my kind. Now, logically, most folks would look to the Soviet-U.S. space race that did this, but (and since this is my writing) my “truthiness” gives the credit from a time and characterization before the fifties and the cosmonauts and astronauts. It had to have been Robert Louis Stephenson and his character, the cook aboard the Hispaniola, Long John Silver headed for the Caribbean and Flint’s Gold. So, it would be my opinion that it was Long John’s Spy Glass that put the telescopes’ popularity (excuse the PUN) on the map. So, onward…
There are three types of telescopes out there on the market: the Refracting Telescope, the Reflecting Telescope, and the Cassegrain (or the tougher name to call it Catadioptric) Telescope. In this article, we will touch base a bit on each. Overall the role of the telescope is to see light at a distance, focus it to a point on a lens (or mirror), the objective lens at the wide end of the Refracting Telescope or to the primary mirror on the Reflective Telescope, then to take that point of light and aim it towards the eyepiece of the Refractor or the primary mirror of the Reflective, where that lens (or mirror) enables the viewer (you) to have the point of light spread across the retina (that back wall) inside the eye. So if you want to see the list of ingredients on a package of processed food in the supermarket from across the street, you’ll need to enter the store to bring it closer to your eye to see, but you technically could see those ingredients from a greater distance with a telescope. Then there is the Catadioptric Telescope (sometimes known as Cassegrain). Most on the market look much like a tin can on a pedestal, but they are a whole lot more. For some, the cost can be prohibitive, but this type of scope combines both the lens and the mirror to provide both reflection and refraction.
The wider planets in the sky—demonstrating the most give off of light are best viewed with a lens based devise (Refractor or Cassegrain), while distance viewing of stars, constellations and astronomical formations are best suited with a mirror based devise (Reflecting or Cassegrain). See what I mean with regard to the Catadioptric/Cassegrain?
Because this is a teaching article, clearly you would want to consider something less than an investment at this point. There are many lesser costing beginner models out there that I will recommend at a later point in our discussion of telescopes, so for now, focus your viewing at a nearby planetarium or online in the two ranges of (1)Planets in our solar system; and (2) Astronomical formations at a distance.