Star-Gazing! What you need to know about Telescopes

1) Performance - What will I be able to see?
Performance is perhaps the most important factor when choosing a telescope. Knowing what you can expect to see through the telescope can help determine which instrument is right for you. The aperture, or diameter, of a telescope governs how much light the telescope can collect. A larger aperture telescope will be able to collect more light than a smaller diameter instrument, and therefore will be able to show you a larger number of night sky objects and more detail on them.

2) Size and Portability
The size and relative portability of a telescope can have a significant effect on how often you use it. While a larger telescope will usually allow you to see more, you may not want an especially large telescope if its size will prohibit you from using it regularly. Our advice is to pay close attention to the size and weight of the telescopes you consider, and try to anticipate how much effort each one will take to set up and use. Although some telescope designs can be bulky, many observers find the extra effort worth it to obtain beautiful views of the heavens.

3) Optical Design - Which telescope design is best for me?
While most people think of a pirate with an eye-patch wielding a long brass tube when we hear the word "telescope", there are actually many different optical designs used to make telescopes. The three most common telescope designs are: refractors, reflectors, and Cassegrains. Each design has different attributes that may make one more enticing to you compared to another, depending on your goals. Let's briefly investigate each design and their main differentiating factors to help you make an informed decision on which one is right for you.



Refractor
Refractors are the oldest telescope design. A small refractor of 60mm to 80mm diameter, referred to as aperture, is usually what most beginners consider buying as a first telescope, thanks to their recognizable appearance and history of good performance. Refractors use a lens system to collect and bend, or refract, light into a cone shape that is focused in an eyepiece for you to view.

A refractor is an excellent choice if you'll be doing most of your stargazing from the city or suburbs, where night skies are moderately light polluted. Since they use a lens system, refractors can be equipped with accessories for daytime use taking in magnified views of terrestrial objects like birds, wildlife, and scenery. Refractors require little to no maintenance, since their optical elements are fixed in place and cannot be misaligned during normal use.

Reflector
As their name implies, reflector telescopes reflect light to a focus point by using mirror based optics. Collected light is reflected off a large dish-shaped parabolic primary mirror, and then reflected again off a smaller secondary mirror so you can focus the view in an eyepiece.


Reflectors provide a big performance punch in a very affordable package relative to other optical designs. All things considered, you will most likely get the most performance per dollar invested out of a reflector design. While affordable, reflectors do require more maintenance, which is an important consideration. Unlike refractor telescopes, the mirrors of a reflector can occasionally become misaligned if the telescope is roughly handled. Because of this, reflectors can sporadically require manual re-alignment, or collimation, of the optics. Don't let collimation intimidate you; any telescope owner can perform this task with a little practice.

Reflectors are most commonly offered in two ways: mounted to a tripod, or attached to a base. Base-mounted reflectors are known as "Dobsonian" designs, named after astronomer John Dobson who unveiled the first Dobsonian base-mounted telescope in 1978. Known as the "best bang for the buck" compared to other telescopes, a Dobsonian or tripod-equipped reflector will provide years of enjoyment for a comparably modest investment.

Cassegrain

Cassegrain telescopes are a relatively recent design compared to refractors and reflectors. Cassegrains are a more advanced and specialized telescope design that uses elements of both refractors and reflectors to bend and reflect collected light. This gives a Cassegrain telescope a very long focal length in a conveniently compact telescope tube.

There are numerous variations of Cassegrain telescopes available to amateurs, all based on the original design attributed to Laurent Cassegrain of France. A Maksutov-Cassegrain (Mak-Cass for short) telescope excels at higher magnification study of relatively narrow-field objects, like the Moon, planets, bright nebulas and star clusters. If you anticipate spending a large amount of time viewing the Moon and planets, a Mak-Cass should be on your short-list of candidate beginner telescopes. Like refractors, Mak-Cass telescopes can be equipped with accessories to provide a correctly oriented daytime view of birds, scenery, and wildlife.