How do you know if a telescope has a large aperture?

Answer 1

The single most important specification for any astronomical telescope is its aperture. This term refers to the diameter of the telescope's main optical element, be it a lens or a mirror. A telescope's aperture relates directly to the two vital aspects of the scope's performance: its light-gathering power (which determines how bright objects viewed in the scope will appear), and its maximum resolving power (how much fine detail it can reveal). There are other criteria to be considered in selecting a telescope, but if you learn only one thing from this article, let it be this: the larger a telescope's aperture (i.e., the fatter it is), the more you will see.

Answer 2

The term "large aperture telescope" is variously used, and includes radio telescopes as well as optical telescopes.

If you are talking about amateur optical telescopes, "large aperture" usually means 12 inches or larger. Remember that the aperture is the diameter of the lens or mirror rather than the size of the outer tube or the hole in the end.

When the subject is large telescopes installed at institutional observatories and used by professional investigators, the term "large aperture" can be a game piece, and it depends on whether you are seeking a grant, selling machine time, addressing the board of trustees, or courting a new girl.

Many professionals consider large aperture optical telescopes to start at about 60 inches, in honor of the 60 inch at Mt. Wilson, and go up from there. In that discussion, a telescope larger than the 200 inch Hale is a "very large aperture..."

In radio telescopes, "aperture" is usually more theoretical. A parabolic reflector larger than 100 feet or so would be considered a "large." They come in all sizes up to a quarter of a mile.

A radio interferometer like the VLA has a theoretical aperture measured in miles.

For lots of information, try an internet search on "large aperture telescope." Also try "national radio astronomy observatory" or "radio interferometer."

Good luck!

Answer 3

A little more complex than measuring the hole in the front.

The aperture is the means by which light is allowed into the scope. Wider is better, but it is also connected to the scope's focal length and ultimately to desired magnification. The lens aperture is usually specified as an f-number, the ratio of focal length to effective aperture diameter. A lower f-stop means more light, but is harder to focus, a "depth-of-field" issue more commonly addressed with cameras.

At $500 (your previous question) you can get some decent priced Dobs, but when you start including "goto" controls and equatorial rotation clock drives, you may have to make some sacrifices.

Your 10-inch Dob is a very nice selection. Once you target a sky object, it would be nice to be able to "let go" and let the telescope automatically track the object with respect to earth's rotation.

Answer 4

From a performance point of view, if your telescope can show 14th magnitude galaxies and nebulae regulary from good skies, it's a large aperture telescope. Galaxies and nebulae are not point sources of light, and because of that a small telescope cannot reveal them, but it can reveal 14th magnitude stars to the user. My 10-inch Dob can show 12th and 13th magnitude galaxies and nebulae, but it is not a large aperture telescope as far as amateur astronmers go. A large aperture telescope for amatuers is something in the 16-inch range and larger.

Answer 5

A 10 inch Dob is a really nice telescope. For amateur astronomy it is larger than average. To really enjoy it try to find a location where the sky is really dark. If you can clearly see the shape of the Milky Way it is probably dark enough to see some interesting things. You wont see bright colors like in Hubble telescope photos, but the more experience you have using your telescope, it the more you will be able to see with it

Answer 6

It will usually list the aperture in inches or millimeters.
4.5" is small but will show you a lot, 5"-6" is still kind of small, 8" is a good amount but not huge, and 10" and up is considered large aperture.

Remember, it's roughly the diameter of the optical tube.

Answer 7

At the front of the telescope (where the light comes in), you will see a hole (or a hole filled by a lens). The diameter of this hole or lens is the telescope's aperture.