Meade StarNavigator 90mm Instruction Manual - Page 15

Intensity Slider Fig. 13: Red Dot Viewfinder intensity slider. Slide the switch to the right to turn on the viewfinder. The switch provides two levels of intensity for the red dot. NEVER point the telescope directly at or near the Sun at any time! Observing the Sun, even for the smallest fraction of a second, will result in instant and irreversible eye damage, as well as physical damage to the telescope itself. Choosing an Eyepiece A telescope's eyepiece magnifies the light gathered by the optical tube. Each eyepiece has a focal length, expressed in millimetres, or "mm." The smaller the focal length, the higher the magnification. For example, an eyepiece with a focal length of 9 mm has a higher magnification than an eyepiece with a focal length of 25 mm. Your telescope comes supplied with a low-powered 25 mm or 26 mm eyepiece which gives a wide, comfortable field of view with high image resolution. Always begin your observations with this eyepiece. Low power eyepieces offer a wide field of view, bright, high-contrast images, and eye relief during long observing sessions. After an object is located and centred in the eyepiece, try switching to a higher power eyepiece to enlarge the image. NOTE: Viewing conditions vary nightly and depend on the site. Turbulence in the air, even on an apparently clear night, can distort images. If an image appears fuzzy and ill-defined, return to a lower power eyepiece for a more well-resolved image. The power, or magnification of a telescope is determined by the focal length of the telescope and the focal length of the eyepiece being used. To calculate eyepiece power, divide the telescope's focal length by the eyepiece's focal length. For example, you may wish to use a 25 mm eyepiece with the StarNavigator102. Look up the focal length of the StarNavigator102 under SPECIFICATIONS: StarNavigator102, page 36. The focal length is listed as 800 mm. Telescope focal length divided by Eyepiece focal length = Eyepiece power 800 Ö 25 = 32 The eyepiece power, or magnification is therefore 32X (approximately). Too Much Power? Can you ever have too much power? If you're referring to eyepiece power (magnification), yes, you can! The most common beginner's mistake is to "overpower" a telescope by using too high of a magnification, which the telescope's aperture and atmospheric conditions cannot reasonably support. Keep in mind that a smaller, but bright and wellresolved image is far superior to one that is larger, but dim and poorly resolved (see below). Powers above 200X should be employed only under the steadiest atmospheric conditions. Audiostar can calculate the best eyepiece for you to use. Try out the "Eyepiece Calc" feature in the Utilities menu. Most observers should have three or four additional eyepieces to achieve the full range of reasonable magnifications possible with the StarNavigator telescopes. See "OPTIONAL ACCESSORIES," page 32. Fig. 15: 26 mm and 9.7 mm eyepieces. Fig. 14a & 14b: Jupiter; example of too much magnification. Looking at or near the Sun will cause irreversible damage to your eye. Do not point this telescope at or near the Sun. Do not look through the telescope as it is moving. 13