Answer to Question 135

A135:

There are two main types of telescopes, Refractors and Reflectors. 

Refractors are the most popular telescope for beginners. They use a lens to gather and focus the light of the object it's pointing at. Using a lens which is made from two elements or more, the refractor reduces false colors. There are two different types of refractor telescopes, achromatic or apochromatic.

Characteristics of Refractor telescopes

• small and compact
• maintenance free
• high resolution (excellent planet scopes)
• can be used during the day for terrestrial viewing without the image being upside down
• expensive for larger models and apochromatic
• less light gathering power than reflecting telescopes because of their smaller size
• awkward to use when pointing straight up (straight up is the best place to view with a telescope)
• false color especially in larger models

Reflectors gather light using a mirror which is curved. The curved mirror concentrates the light and is then magnified by an eyepiece. Newtonian reflectors (invented by Sir Issac Newton) can be identified by the eyepiece protruding from the side of the telescope. These are the most common and cheapest to buy. Other types of reflectors incorporate a front lens which corrects the incoming light first before hitting the main reflective mirror. These front lenses are called corrector plates and the different types used determine the type of reflecting telescope. The more popular types are the Schmidt-Cassegrain and the Maksutov-Cassegrain.

Characteristics of Reflecting telescopes

• excellent light gathering power - the bigger the better
• cheapest per centimeter of aperture
• wider field of view than refractors
• some maintenance required (re-coat the mirror faces every 8-10 years, re-align mirrors if necessary)
• optics are not enclosed, but can be cleaned occasionally
• lower resolution due to secondary mirror obstruction, generally suited better for faint objects

Advice for First Time Telescope Buyers...Contd (7)

Number 7: Where to buy a Telescope

There are a number of places to buy a telescope... however I advise against purchasing a telescope at a department store (Wal Mart, K-Mart, Toys R Us, etc)! Astronomy (today) is a fairly niche interest and as a result you will almost certainly have to buy your scope from an on-line vendor. There are a few towns that have superb telescope stores, but they are very rare and chances are you don't live anywhere near them.

The following is a list of on-line/mail order outfits I have personally dealt with, and recommend without hesitation (please note that there are many more I have not dealt with that are probably just as good!):

Advice for First Time Telescope Buyers...Contd (6)

Number 6: Computerized Telescopes

Many telescopes available today employ electronics, the main purpose of which is to help you locate objects in the sky. So called "Go to" telescopes locate things for you (you dial them up on a hand held controller). A second type (less common) type of computerized teelescope is called "push to". These will also help you find objects, but you physically move the scope while looking at a readout that guides you to your desired target.

Advice for First Time Telescope Buyers...Contd (5)

Number 5: What Brand Telescope is Good?

In the beginner telescope market, this question has become clouded in the last 15 years or so (the good news is that there are more choices than ever before and plenty of great beginner scopes). Meade and Celestron are two major telescope companies; in years gone by all the telescopes offered by these companies were good to excellent. That has changed today, unfortunately the name Meade or Celestron on a telescope no longer guarantees that the scope is a good one. 

Advice for First Time Telescope Buyers...Contd (4)

Number 4: Telescope Quality

As far as beginner telescopes are concerned, there are many telescopes on the market that are best avoided. Fortunately there are more great choices today than ever before (and at very reasonable prices). Ideally you will spend $500 to get started with an excellent package, however I know that this is out of reach for many. Fortunately there are some nice choices in the $100 range (stick with the ones I recommend however, do not buy any old $100 scope you find)! Many beginner telescopes make performance claims that are preposterous, and are of very poor mechanical and optical quality. You are better off buying a simple (but well made) telescope. In other words, buy a telescope where the money has gone into basic functionality (good optics and a good mount). Telescopes to be avoided are easily identified, since they come standard with numerous (but often useless) accessories (more on this below)!

Advice for First Time Telescope Buyers...Contd (3)

Number 3: Use LOW magnification, and make sure your scope is properly adjusted!

If you take away only one thing from reading this page, let it be this : Magnification is NOT a measure of a telescope's quality or capabilities! Many beginning astronomers think that high magnification is they key to great viewing. This is a common misconception. A telescope's "power" is a function of the diameter of its mirror (or lens). In general, bigger is better for telescopes!

Advice for First Time Telescope Buyers...Contd (2)

Number Two: Don't blame the telescope for things it can't control!

Many beginners don't realize that a telescope's performance is often at the mercy of local ambient conditions. Other than the obvious (clouds, fog, etc.), there are several other major factors which limit how much can be seen.

Light pollution is by far the biggest problem facing today's astronomers. Light Pollution has (for all practical purposes) completely ruined the skies in and around of just about every moderate to large city (this means that unless you live out in the country the only things you'll probably be able to see well are the Moon and bright planets). Light pollution is caused by excessive amounts of and/or poorly designed outdoor lights. Light pollution will not degrade the viewing of the Moon and planets, but it can seriously limit the number of non-solar system objects you might otherwise see (objects such as galaxies, star clusters and nebulae). Light pollution has invaded almost all populated areas of the country. Often, the only remedy is to drive to a dark location, generally 50 to 100 miles or so from any major city (and even at this distance evidence of light pollution may remain readily visible). For more information on light pollution, see my article dedicated to this topic: Light Pollution. For a very comprehensive treatment of light pollution, see the International Dark Sky Organization's web site at www.darksky.org.

Advice for First Time Telescope Buyers

If you are new to astronomy and contemplating the purchase of your first telescope, this page will help you to better understand what to look for in a telescope and what to expect from it. There are many telescopes aimed at beginning astronomers, and first time buyers are often overwhelmed by all the choices, brands, etc. This page will arm you with the basic information you will need to get off to a good start in astronomy.

The contents of this page applies to small to medium sized, beginner (or "first") telescopes. By small, I mean 2.4 inch (60mm) to roughly 3.5 inch (80 to 90mm) refractors, and 4.5 to 6 inch (100-150mm) reflectors . Telescopes in this beginner class typically sell for around $150 to $600. Quality starter telescopes are available from a number of manufacturers. The buyer should be aware that there are quite a few very poor quality telescopes in the marketplace; these are most often found in "department stores". It is hoped that the information on this page will help out prospective new astronomers and to advise them not to expect too much from a small telescope. 

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First...BEFORE you buy a telescope!