How to Choose a Telescope

Portability and Practicality

Choosing a telescope demands several factors be considered. There's no point having a great big telescope if its so hard to set up that you don't often feel inclined! Having handled hundreds of scopes I can assure you the big ones are not easy to handle and can be so large and heavy as to risk damaging your back.

The easier the telescope is to use, the more inclined you will be to use it and therefore the greater enjoyment you'll get from it, so make sure you take ease of use into consideration.

You must also consider where most of your viewing will be done as city and suburban light pollution tends to make effective use of large telescopes difficult whereas in a good dark sky location you will want to reach further than a small telescope will allow. If you'll be traveling to the middle of nowhere the ease of transport becomes an important factor.

Budget Factors

Essentially, the greater the diameter of your telescope the more magnification you can achieve with it, so in broad sweeping terms I'd advise going for the largest aperture your budget allows if you want to see "as much as you can".

A small beginners refractor might cost about a hundred dollars but should allow decent moon views and a bit of casual stargazing. If you're after 'power' (I'll come back to that) then go for the largest aperture telescope you can afford but be aware that large apertures are not so good in light polluted areas like the suburbs of most cities. Again, you must bear the practicality and portability thing in mind here! At the upper end of the scale some telescopes cost several thousand dollars though are still classed as 'amateur equipment'

Purpose and Power

So what is it you're hoping to see or do with your choice of telescope anyway? If you are hoping to see sights like some of those beautiful posters then forget it unless you're going to borrow the Hubble for a while. Be realistic in your expectations.

A small refractor will be perfectly adequate for observing the moon, even binoculars can give great moon views.

A general rule of thumb is that from about 4 inches (102 mms) aperture upwards things start to get interesting! In good conditions you'll be able to see a ring around Saturn, maybe the red disk on Mars, a band of colour around Jupiter.

If you're after the most aperture for your dollar then the Dobsonian type telescopes offer large apertures at just a few hundred dollars. These are quite large beasts mounted on simple turntables that can produce highly magnified images with good clarity.

If you're looking to get into astrophotography then you'll need a combination of good aperture and motorized tracking to keep the object in center focus so think big budget for a big catadioptric (see more on those below)!

Be wary of telescopes advertised as having so and so 'power' this is a poor way to market a telescope as magnification is actually achieved by the eyepiece you use and there are several things to consider there too.

A useful thumb rule on power is to think of the maximum magnification you an achieve as being twice the aperture size in millimeters (i.e. a 150mm telescope can achieve up to 300x) This is a rough maximum, in practice staying well below the maximum tends to give a better overall image.

Power and Simplicity Combined -
See the Meade 10" LightBridge Truss-Tube Dobsonian Telescope

Power and Sophistication Combined - The Nexstar 8SE Telescope

Refractors have their primary lens at the front end of the tube bringing light to a focus point at the eyepiece on the back end of the telescope.

This type was the first astronomical scope. They tend to produce nice sharp images and are usually the better choice in the suburbs where light pollution is to be contended with.

Large aperture refractors can also be quite long and difficult to use, they are also expensive due to the amount of glass work involved so tend to be relatively rarely used in practice.

Check out more on these types of telescopes at TelescopeChoice.com:
Refractor Telescopes

Reflectors use a mirror for gathering light then reflect the light to the eyepiece via another small mirror (the secondary mirror).

Reflectors tend to offer a combination of medium to large apertures with ease of use and are most often used for amateur astronomy.

Very large reflectors are sometimes mounted on simple turntables known as Dobsonian mounts. They are easy to use and their large apertures offer excellent deep-sky viewing, if you are in a good dark sky location.

Check out more on these types of telescopes at TelescopeChoice.com:
Reflector Telescopes

Catadioptric telescopes such as the Schmidt-Cassegrain & Maksutov-Cassegrain, combine relatively large apertures with short tubes for ease of handling and portability. They achieve this by reflecting the gathered light twice inside the tube before passing it out to the eyepiece.

Catadioptric telescopes are often mounted on motorized and computerized mounts known as go-to mounts, making navigation a matter of entering the targets name or catalogue number into the hand-held controller.

Their more complicated construction tends to make them expensive but their all round capabilities make them very popular with keen amateurs.

Check out more on these types of telescopes at TelescopeChoice.com:
Catadioptric Telescopes

The telescope is completely useless without an adequate means of supporting it to allow the observer to use it. Simple mounts such as the alt-azimuth mount are often used for land viewing and casual astronomy. They only allow up-down and side to side movement of the telescope. The Dobsonian mount mentioned earlier for large reflectors is actually a type of alt-az mount.

Equatorial mounts allow the telescope tube to move through an arc which is essential for tracking an object as it moves through our sky. They can be motor driven through a hand controller. There are many variations popular with serious astronomers and astro-photographers.

No matter how high the quality of the telescope, it will be limited by the quality of the mount. Cheaper telescopes come with cheap mounts that allow the telescope to move easily in wind or with vibrations from passing traffic. You will want a mount which is steady and sturdy enough to take the weight of your telescope comfortably, this becomes especially important for deep sky observing or astrophotography.

Refractors Pros: Sharp images, good in light polluted areas, little maintenance, can be used for land viewing to

Refractors Cons: Chromatic abberation (false colours) in cheaper models, large apertures often impractical due to bulk and cost

Reflectors Pros: No chromatic aberration, less bulky than refractors of same apertures, more aperture for the cost, particularly the Dobsonian models

Reflectors Cons: Some loss of contrast so images not as sharp, need to be maintained and collimated (mirror alignment)

Catadioptric Pros: Generally compact and portable for the aperture size, easily computer driven for navigation, less expensive than equivalent refractors

Catadioptric Cons: Some loss of image brightness, Can be prone to dew formation which hinders viewing, more expensive than equivalent reflectors