Beginner Level - Suited for a wide range of uses, these products are simple to operate and set up. Some initial assembly may be required depending on the type of product. Optical instruments with this rating will have very good optical and mechanical quality. Great for families, young people, and folks who don't want to mess with equipment and complexity. Beginning level telescopes will show you countless lunar craters, Saturn's rings and a myriad of star clusters and nebulae! Referring to the manual is recommended.

Intermediate Level - These products offer higher performance and more advanced features than Level 1: Beginner 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 Level - These products provide the best performance but may require more skill to master and appreciate. Optical instruments with this rating have exceptionally fine optics and mechanics. Some are easy to use but might be on the large or heavy side. Some are intended for specialized uses. These products will appeal to the more technically inclined. Referring to the manual is highly recommended.

"Diffraction Limited" means that the limits of image detail are determined by the physical properties of light, and not by optical defects in the telescope.

Instead of a single thumb screw locking the eyepiece in place, a brass ring compressed by a thumb screw secures the eyepiece. This spreads clamping force over a larger area of the eyepiece's barrel, which provides a better connection. The compression ring also prevents the tip of the thumb screw from producing unsightly scratches and divots on the eyepiece barrel.