Beginner - Suited for a wide range of uses, Level 1 telescopes are simple to operate and set up. Some initial assembly may be required. Very good optical and mechanical quality. Great for families, young people, and folks who don't want to mess with equipment but just want to take a look. Any of these scopes will show you countless lunar craters, Saturn's rings and a myriad of star clusters and nebulas! Referring to the manual is recommended.

Intermediate - These scopes offer higher performance and more advanced features than Level 1 models. They typically take a bit longer to learn and need some set-up or adjustments. But anyone with the slightest technical bent will have no problem getting familiar with these models. Referring to the manual is recommended.

Advanced - These scopes provide the best performance but may require more skill to master and appreciate. They have exceptionally fine optics and mechanics. Some are easy to use but are but on the large or heavy side. Some are intended for specialized uses. These scopes will appeal to the more technically inclined. Referring to the manual is highly recommended.

Expert - Expert telescopes offer uncompromising optical and mechanical quality for the most demanding amateur astronomer. They may be technically involved or designed for specialized use, such as astrophotography or detailed deep sky observation. They carry a premium price, but are designed to provide the ultimate performance in the field. Referring to the manual is highly recommended.

A measure of the enlargement of an object seen through an optical instrument. More specifically, it is a measure of the angle subtended by an image viewed with optical aid divided by the angle subtended by the same object without optical aid. Magnification is determined by dividing the focal length of the telescope (or binocular) by that of the eyepiece. Hence a telescope with a 1200mm focal length and an eyepiece of 40mm yields a magnification of 30x. The human eye is considered 1x magnification.

The field of view expressed as part of a 360-degree circle. Holding your pinky finger out at arms length is approximately 1-deg wide. To convert this to the linear measurement of "feet at a thousand yards", multiply by 52.5. For example, at 1000 yards distance, a 7-deg binocular will see a width of 367.5 feet (7 x 52.5)

The distance, measured in millimeters, between the observer's eye and the eyepiece lens in which the entire field of view remains visible. Eye relief varies with the optical design but generally increases with decreasing magnification. Long eye relief is advantageous for observers who wear glasses, as they don't have to put their eye directly on the eyepiece to see the entire field of view, nor do they have to remove their eyewear.

The minimal distance at which a binocular and/or spotting scopes can attain focus. Near focus is an important quality for bird watchers and wildlife devotees who want to get as close as possible to their quarry.

Lowest useful magnification is the power at which the exit pupil becomes 7mm in diameter. Powers below this can still be reached with the telescope to give wider fields of view, but the image no longer becomes brighter at a lower power. This is due to the fact that the exit pupil of the telescope (the beam of light exiting the eyepiece) is now larger than the average person's dark adapted pupil, and no more light can fit into the eye.