I want to buy a telescope!?

Question

I want to buy a telescope for sky watching. I am physics student so you can guess which sort I need. I have no idea what should be the configuration of a telescope to make decent observations.

Please give me some information on the configuration and name if possible!

Answer 1

Because you are a physics student, I will explain in depth. There are many different kinds of telescopes, each suited for different purposes. First you have to decide what you want to look at. Some telescopes are good for planetary viewing, some are good for deep space viewing, and some have wide fields of view and are good for star field and nebula viewing. You also need to decide how much you want to spend. If you don't have at least $150 then just buy some good binoculars. Here is a little about telescopes and what kind you should be looking for.

There are refractors, reflectors, catadioptrics, and some more exotic designs.

There are three very important words you must know as a physics student and to buy a telescope.

Aperture: Aperture refers to the diameter of the telescopes primary lens or mirror. The larger the diameter the more light the telescope can collect, the brighter dim objects appear, and the more things you can see.

Focal length: This is the distance from the primary lens or mirror, to where the lens or mirror actually focuses the light.

Focal ratio:This refers to the aperture divided by the focal length, usually expressed as f/# where the # is actually the focal ratio. Some common ones are f/4.5 and f/6. The smaller the number, the wider the field of view, but there will be more edge distortion, and the telescope will be more sensitive to optical misaligments. The higher the number, the narrower the field of view, the less edge distortion....there's actually more to it than that, which is explained here: http://www.brayebrookobservatory.org/BrayObsWebSite/HOMEPAGE/forum/longvsshortf-ratios.html

Telescope types:
Refractors use a large lens up front and you view through the back. It is difficult and expensive to make large, high quality lenses so refractors are typically smaller in aperture. Lenses by themselves suffer from chromatic abberation. As you might know (or will learn), different wavelengths, or colors, of light diffract to different degrees when crossing from one medium to another. When entering a lens or prism, red will bend the least and blue/purple the most. In an uncorrected refractor, this causes the image to have a red halo on one side and a blue halo on the other. To correct for this, systems of lenses are often used. A partially corrected refractor is called achromatic and an almost fully corrected one is called apochromatic. Because of their small size yet crisp optics, apochromatic refractors are ideal for planetary and star cluster viewing.

Reflectors:
Reflectors use mirrors instead of lenses. They have a parabolic mirror in the back of the telescope which reflects the light to a small secondary mirror near the front of the telescope, which in turn reflects the light to the eyepeice in the side of the telescope. Most reflectors are Newtonian style reflectors and sit on a german equatorial mount. These mounts move in the natural motion of the sky and are ideal for astrophotography setups. Some reflectors are Dobsonians. These sit are usually on atr-azimuth mounts that sit on the ground. Alt Azimuth mounts need to be moved in steps (up/down side/side) but are far cheaper than german equatorial mounts, allowing for Dobsonians to have larger apertures for less price.
Reflectors are the most cost effective telescopes to make and because large apertures can be produced and sold at affordable prices, they can be used for local or deep space viewing.

Catadioptrics: Catadioptrics are various configurations of telescopes that use what is typically a concave spherical mirror in the back which reflects light to a seoncdary mirror near the front which in turn reflects the light either to the eyepeice in the side (Schmidt Newtonians) or back through a hole in the middle of the primary mirror to the eyepeice in the back of the telescope.
Spherical mirrors are easy to make and give a wide field of view, but they produce an error called spherical abberation, so catadioptrics have a corrector plate at the opening of the tube to fix this. With the exception of Schmidt Newtonians, catadioptrics such as Schmidt Cassegrains, where the light goes back through a hole in the primary mirror, have the advantage of long focal lengths in short tubes. This makes them compact enough to keep in the livingroom but with the advantages of long focal lengths if that is what you want.

Some catadioptrics come on german equatorial mounts but this makes them more expensive so most come standard on form mounts. Fork mounts move like alt-azimuth mounts but unlike those used by Dobsonians, can be easily equipped (if they don't come so already) for astrophotography.

The two most common types of catadioptrics are Maksutov Cassegrains and Schmidt Cassegrains. Maksutov Cassegrains are typically only available in smaller apertures so for most deep space viewing, Schmidt Cassegrains are used.

Some people believe refractors to be superior to reflectors, pointing out the fact that the secondary mirror in reflectors (and catadioptrics) creates an obstruction causing less light to be collected. It is true that a refractor will collect slightly more light than a reflector of the same size, but good luck finding a defect free apochromatic refractor under $10,000 that will collect as much light as a 10" reflector.

There's also telescopes with features such as goto systems, navigation systems, and GPS.

Conclusion: For about $400-$900 used you can buy a Celestron or Meade 8" Schmidt Cassegrain with a motor drive for astrophotography or even a goto system and for $200 you can buy a CCD camera. This will give you a decent view of planets and some deep space objects. Many of the objects not bright enough for you to see very will can be photographed (that's what researchers do anyway)

For about the same price used, you can get a 10" Dobsonian which you can't do astrophotography with unless you build or buy an equatorial platform for it but you'll be able to see more deep space objects under dark skies with your own eyes.

Meade, Celestron, and Orion are all reputable companies. If you have the money and you care more for refined optics than aperture, Astro-Physics and Takahashi might be your cup of tea.

If you have about $30,000 and have always dreamed of a giant telescope then JMI makes a 40" trust tube telescope that you'll have to buy a truck to haul :-)

Answer 2

Meade or Celestron are good brands although they're fairly highly priced. I own a Meade ETX-125AT myself and the quality is amazing if you are thinking about doing lunar and planetary study. If you want something that can give you good nebulae and deep space results then you should go for something with a bigger aperture (like an 8" or 10"). With telescopes, the bigger the aperture the better as it allows the scope to receive more light and give you a clearer image (especially with deep space objects).

Answer 3

You should buy a reflector telescope not a refractor telescope, you will get more "bang for the buck" if you will. You can read all about the different kinds here, http://www.telescope.com/jump.jsp?itemType=GATEWAY&itemID=4

Answer 4

Emily I additionally comply with connect a membership.to boot getting solid innovations and searching via diverse scopes. somewhat generally they are going to own loan you a scope for unfastened, or you will desire to purchase a used scope from a member,

Answer 5

If you can find one, buy a used Criterion RV6.

Answer 6

Meade is one company