Welcome to the Telescope Site

Choosing a Telescope

There are many factors to consider when choosing a telescope. Making the right decision can be the difference between it ending in the closet for years vs spending many nights in the backyard or observing site. There are a lot of different types of telescopes and each has a specialty. This web site contains several pages that will help you make the decision that is tright for you. Before you head out to make your purchase I urge you to at least read this first page.

While cheap department store telescopes are often sold by marketing their "power" or magnification, the truly important factors are aperature and configuration.

The first think you will want to do is visit out introduction to telescopes page that explains the basic terms use when describing telescopes.

Telescope Features

Once you have decided that you want to buy a telescope, you will have many types to choose from, falling into many price ranges.

• Telescope Configuration
• Mounts
• Eyepieces
• Finders
• Filters

Telescope Types

There a several types of telescopes available. These telescopes are also available on varois mounts, The telescope type of telescope you choose wiil depend on what you plan to use it for. For example for basic observing you may choose an inexpensive reflector. For astrophotography you may choose a refractor on an equitorial mount.

Newtonian reflectors are great all-around scopes, offering generous apertures at affordable prices. They excel for both planetary and deep-sky viewing. Of course, the larger the aperture, the more you’ll see. Smaller, 3" and 4.5" equatorially mounted Newtonians will provide a nice “survey” of celestial luminaries, and they’re plenty portable. Six-inch and 8" Newts have enough aperture to deliver captivating images of fainter fare-clusters, galaxies, and nebulas-especially in a reasonably dark sky. The tradeoff is their bulk and weight — something you should definitely take into account before you buy. But a 6" Newtonian on a Dobsonian mount is easily manageable by one person, and makes a wonderful beginner scope. Dobsonian-mounted reflectors have lower price tags than their equatorial counterparts, starting in the mid-$300s for a 6" Dob.

A small, quality achromatic refractor of 60mm to 80mm aperture makes a fine starter scope for observing the Moon and major planets. They’re inexpensive ($100 to $350), portable, and maintenance-free — all desirable factors if you’re just “testing the waters” of the hobby. Their small apertures aren’t well suited for faint deep-sky objects, though. If nebulas and galaxies are your main interest, a Newtonian reflector or Schmidt-Cassegrain is the way to go. Moving up to a 90mm or 100mm refractor will snare more objects and provide better performance, for a higher price. Renowned for crisp, sharp images, refractors are the priciest per inch of aperture of all telescope types. A refractor is the scope of choice if you will be doing most of your stargazing from city or suburbs, where the night skies are moderately light-polluted. Here, more aperture doesn’t gain you much, since viewing is restricted mostly to the Moon and planets. In fact, a big scope would only amplify the skyglow, yielding poor washed out images.

Telescope Mounts

The type of mount you choose for your telescope is just as important as what type of telescope you choose. Some mounts are bettor for tracking object, others are easy to manuever when you are hopping around the sky.

Telescope Eyepieces

Selecting an eyepiece to use with your telescope depends on what type of telescope and what you intend to look at. Wide angle eyepieces are great for looking at large objects like open clusters or large nemulae. Other eyepieces are better for looking at planets since magnification is more important than field of view. This page explains the differences and why you would select one over another for viewing different objects.

Try Various Telescopes Before You Buy

The most important thing I can stress when thinking about the purchase of a telescope is to visit a local amateur astronomy club. You will be able to try some different types out and ask questions. talking with amature astronomers that have used different types of telescopes will certainly help you make a good choice when choosing a telescope to fit your needs.

Amateur astronomy clubs exist in every state. Every club I have visited has several telescopes for use by members. Clubs also have "public nights" where they bring the telescopes out for the public to use. If you attend, don't be afraid to ask questions about the equipment.

Usually there are telescopes outside with volunteers ready to assist you. If it is not crowded, ask if you can't try finding something in the scope. Ask if they have a suggestion for an object to find. Ask them to step you through the process of hunting for the object and zeroing in on it. Ask them what types of telescopes they own and which ones they use most often.

Becoming a member of a club also has it's rewards. Clubs have "member nights" which are less crowded and give you an opportunity to work hands on with a seasoned astronomer.
 

Telescope History

The earliest known working telescopes appeared in 1608. The design of these early refracting telescopes consisted of a convex objective lens and a concave eyepiece. Galileo used this design the following year. In 1611, Johannes Kepler described how a telescope could be made with a convex objective and eyepiece lens and by 1655 astronomers such as Christiaan Huygens were building powerful but extremely large and unwieldy Keplerian telescopes with compound eyepieces.

Isaac Newton is credited with building the first "practical" reflector in 1668 with a design that incorporated a small flat diagonal mirror to reflect the light to an eyepiece mounted on the side of the telescope. Laurent Cassegrain in 1672 described the design of a reflector with a small convex secondary mirror to reflect light through a central hole in the main mirror.

The achromatic lens, which greatly reduced color aberrations in objective lenses and allowed for shorter and more functional telescopes, first appeared in a 1733 telescope made by Chester Moore Hall, who did not publicize it. John Dollond independently developed achromatic lenses and produced telescopes using them in commercial quantities, starting in 1758.

Important developments in reflecting telescopes were John Hadley's production of larger paraboloidal mirrors in 1721. The process of silvering glass mirrors was introduced by Léon Foucault in 1857. The adoption of long lasting aluminized coatings on reflector mirrors in 1932. Almost all of the large optical research telescopes used today are reflectors.
 

The most important feature of any telescope not it's magnification, is its light gathering capability, or aperture. The more light gathered, the more you’ll see. For example, a 6" mirror/lens is 2-1/2 times the diameter of a 60mm mirror/lens, yet it gathers 5-1/2 times more light. The brightness-boost delivered by the bigger, high-quality optics seems to yield dramatically finer detail, simply because previously invisible structure gets promoted to the visible~or in other words, the resolving power is increased.

This infomation is provided form my choosing a telescope pages on my amature astronomy site astro-observer,com