Telescope purchasing?

Question

What do i look for when purchasing a telescope, I am looking to spend around $300 or something maybe more. I want a telescope where i can switch lense pieces.

Answer 1

Be wary of power

One of the things that is usually promised is incredibly high power. Be aware that virtually any telescope can provide you with, say, 500-power. Yet in most cases, such an advertised magnification is well beyond the practical maximum magnification of the telescope.

The result: big, blurry images.

A 2.4-inch refracting telescope, for example, should never use more than 120-power (the rule of thumb is 50-power per inch of aperture). In fact, for such a telescope, the most rewarding views will probably come using one-half of the practical maximum magnification (60-power).


Find stability

Another common problem is the telescope mounting, which for most "off-the-shelf" instruments is usually lightweight and unstable. Such mountings are, in turn, attached to a wobbly tripod. A telescope can have the finest optics in the world, yet can be rendered totally useless if the mount is so poor that the image can’t be held in place.

But of course, the uninitiated (usually that "space-minded child") will want to "test drive" the telescope at the highest possible magnification. The result will be an enlarged and hopelessly fuzzy image that will be virtually impossible to keep in the telescope’s field of view thanks to its defective and unbalanced design.

Before you know it, that "practical learning tool" has ended up in the back of a closest or up in the attic, never to be seen again!

More tips

If you still have your heart set on purchasing a telescope, here are a few good tips to follow:

Go to your local bookstore or newsstand and browse through one of the various astronomy magazines where well known and reputable manufacturers advertise astronomical telescopes.
Many planetariums across the country offer courses on "How to Use a Telescope." Such classes typically assist both the prospective purchaser and those who wish to get the most out of an instrument that they already have.

Contact local astronomical societies and attend star parties and other, similar events where he or she can look through various telescopes and talk to their experienced owners. Such gatherings are ideal "showrooms" for commercial as well as home-built telescopes.

Try this

I’m about to make a suggestion that most prospective telescope buyers – especially those neophytes of astronomy – do not want to hear: Consider the merits of binoculars before moving up to a telescope.

Some might think that binoculars are a bit of a come down from a telescope, but the fact is that for certain aspects of sky watching they are the best instrument.

Binocular vision provides our central image processing system (the brain) with confirmation of what both of our eyes are seeing. In effect we improve our signal-to-noise ratio by using two eyes. The brain filters out the random impulses from each eye and leaves us with a better view of the real object. The result is increased contrast (about 40 percent) and the ability to see fainter objects.

Binocular tips

Most preferable for star gazing are the 7x50 "night-glasses," although my own personal preference is a pair of 7x35 binoculars that give a much wider-than-normal field of view. The first number states the power of the binocular (7 power), while the second number represents the diameter of the objective lens in millimeters (35 or 50).

http://www.space.com/spacewatch/041126_telescope_tips.html

Answer 2

The most important specification for any astronomical telescope is the aperture, which is the diameter of the primary lens or mirror. A larger aperture lets you see fainter stars, nebulae, and galaxies, and will also show sharper images. Virtually all astronomical scopes take standard interchangeable eyepieces.

You'll get the most bang for the buck with a "dobsonian" telescope. This is a Newtonian reflector on a simple alt-azimuth (tilt-swivel) base.

Also, be careful where you buy the telescope. Your best option is to buy from a store that specializes in astronomical telescopes. Avoid Walmart, sporting goods stores, camera stores, and eBay. These sorts of places places often sell telescopes that sound like a good deal but are actually optically and mechanically inferior.

Orion Telescopes and Binoculars (see first link below) has a good selection of beginner-to-intermediate scopes, and the quality of their scopes is generally good. The Yahoo telescopes group and the forums at Cloudy Nights are good places online to look for more advice and information. If there's an astronomy club near you, that can be a good source of information, especially if they have public star parties.

Answer 3

You should be able to switch eye peices in all telescopes.

What you should look for in a telescope really depends on what you want to do with it. In general though, a good telescope will have a decent amount of light gathering power. This is called aperture. The larger the diameter of the primary mirror in reflectors, or objective lens in refractors, the more aperture it has, making objects brighter.

You want to make sure you buy a brand with "diffraction limited optics" like Meade, Celestron, or Orion. This means that they test the quality of the optics and make sure they meet rigorous standards before they sell them.

A telescope should come with a sturdy mount as well.

For $300, if you buy used, you can get a 10" dobsonian, 6" or 8" Newtonian, or maybe a 60mm achromatic or apochromatic reflector. I highly recommend buying used because you really can't get much aperture for $300 when you buy new, especially if you want bells and whistles like goto or navigation systems. If you were to buy new, for $300 you may be able to get a 4.5" Newtonian, 4.5" is just enough to see the tip of the iceberg as far as deep space objects go, but will probably leave you wishing you had something bigger.

I've posted a few other answers on telescope where I've gone into more detail about the different types and where to get good used ones if you want to look them up.

Answer 4

You can switch lenses on any telescope. Reflecting telescopes can give you a bigger diameter at a shorter focal length and cheaper price, so I would suggest that. The best kind to get commercially are Schmidt-Cassegrain as they combine a little bit of Newtonian reflecting telescopes and a little bit of refracting to get the most light gathering power.

How far you can see is _not_ determined by the length of your telescope, but by the diameter. The greater the diameter, the greater the light gathering power. We do not know how to grind parabolic lenses so refracting telescopes tend to get chromatic aberration (color splitting) caused by their spherical shape. Reflecting telescopes use parabolic mirrors and have inherently better images, though usually, the aberration in reflectors isn't that bad because you usually don't have diameters that large on refracting telescopes. Plus, you can remove the mirrors and have them resurfaced every several years or so and basically have a telescope that lasts. Also refracting telescopes, if you get a larger one (i.e. comparable to a nice reflector you could get) get very long and you don't want to have to use a step stool or ladder while observing or limit your light gathering power by going with a small diameter.

Answer 5

Go to a good camera/lens shop and ask. I used a reflection telescope, and refraction telecope. The reflection telescope is large and can be cumbersome, and that one was pretty cool. The refraction scope is cool with a large tripod. To my understanding telescopes with glass lense pieces are considerably better than the others, excepting price range.

Answer 6

The 2 most important point should be:
1) how "far" you can see which is determined by the length of the telescope
2) how bright the objects you are looking at show up (that's going to be how large the scope is

Some of the fun features you can find are automated telescopes although i don't know how accurate they truly are.

here is a good site you can get info and shop.

http://galileo.telescopes.com/

Have fun scoping the skies!