# Knowledge Base | How To Use A Telescope Correctly

The number on the Ocular/ eyepiece is the focal length of the eyepiece.

The magnification of any telescope eyepiece used with your telescope will be the focal length of the telescope (consult your manual) divided by the focal length of the eyepiece. A telescope with a focal length of 1200mm will yield a magnification of 60x when you insert a 20mm eyepiece into the focuser. A telescope with a focal length of only 600 mm, however, will yield only 30x when used with the same 20mm eyepiece.

A low magnification eyepiece has a wider field of view (the amount of sky you see when looking through the eyepiece) than a high magnification telescope eyepieces. The low-magnification eyepiece therefore makes it easier to "capture" an object you are trying to find in your telescope. Your lowest magnification eyepiece will also give you the sharpest image as well as the brightest image. Once you have located an object with your low magnification eyepiece, move the telescope so the object is as close to the center of the telescope field of view as possible. Replace the low magnification eyepiece with one of higher magnification. If the object is not visible after you have changed to the high magnification eyepiece, go back to the low magnification eyepiece and start again.

A low magnification eyepiece has a wider field of view (the amount of sky you see when looking through the eyepiece) than a high magnification telescope eyepieces. The low-magnification eyepiece therefore makes it easier to "capture" an object you are trying to find in your telescope. Your lowest magnification eyepiece will also give you the sharpest image as well as the brightest image. Once you have located an object with your low magnification eyepiece, move the telescope so the object is as close to the center of the telescope field of view as possible. Replace the low magnification eyepiece with one of higher magnification. If the object is not visible after you have changed to the high magnification eyepiece, go back to the low magnification eyepiece and start again.

A basic law of optics states that as magnification increases, image brightness decreases. In fact, if you increase magnification enough, an object will become too faint to see. This happens sooner in a small telescope than large telescopes.

A Barlow lens is a lens that you use with your eyepiece. A Barlow lens will double (2x Barlow) or even triple (3x Barlow) the magnification of any eyepiece that you attach to it. To use a Barlow lens, remove the eyepiece from the focuser, insert the Barlow and then insert the eyepiece into the Barlow. Remember, though, that a Barlow is best used with low magnification (long focal length) eyepieces. When used with high magnification eyepieces, it may produce more magnification than your telescope can use.

The telescope is not only magnifying the object you are observing in the sky, it is also magnifying the earth's rotation! The more magnification you use in your telescope, the quicker an object drifts out of the field of view. Manual telescope mounts will require you to continually "recapture" the object by moving your telescope slightly. Motorized mounts move the telescope for you and keep the object in the eyepiece.

Use only enough magnification to provide a useable image. When you reach a point where the image has become so blurred as to lose useful detail, you are using too much magnification! At what point this happens depends on the object you are observing, the seeing conditions (atmospheric clarity and stability) and the size of your telescope (you can get more magnification out of a large telescope before images begin to blur).