Meade ETX-80AT-TC Instruction Manual - Page 28

North Declination at 0˚ Pointer Fig. 21: Alt/Az Home Position. ADVANCED FEATURES Terrestrial Observing The ETX-80AT makes an excellent high-resolution, terrestrial (land) telescope. Viewing terrestrial objects requires looking along the Earth's surface through heat waves. These heat waves often cause degradation of image quality. Low power eyepieces, like the MA 25mm eyepiece, magnify these heat waves less than higher power eyepieces. Therefore, low power eyepieces provide a steadier, higher quality image. If the image is fuzzy or ill-defined, reduce to a lower power eyepiece, where the heat waves do not have such an effect on image quality. Observing in early morning hours, before the ground has built up internal heat, produces better viewing conditions than during late afternoon hours. Astronomical Observing Used as an astronomical instrument, your telescope has many optical and electromechanical capabilities. It is in astronomical applications where the high level of optical performance is readily visible. The range of observable astronomical objects is, with minor qualification, limited only by the observer's motivation. Sidereal Rate As the Earth rotates beneath the night sky, the stars appear to move from East to West. The speed at which the stars move is called the sidereal rate. If the telescope is aligned, the motor drive is designed to rotate the telescope at the sidereal rate so that it automatically tracks the stars. This tracking makes it easy to locate objects and keep them centered in the telescope's eyepiece. Alignment (Mount) The telescope's mount permits the movement of the telescope in both Altitude (vertically) and Azimuth (horizontally). In order to automatically track a celestial object, the mount must be properly aligned. Easy Alignment is described on page 18. Alt/Az Alignment One-Star Alt/AZ Alignment or Two-Star Alt/AZ Alignment allows you to choose the alignment stars during the alignment procedure. The stars are chosen from AutoStar's database of alignment stars. The database displays after One-Star Alt/Az or Two-Star Alt/Az Alignment is selected. . The term "Alt/Az." is frequently used to refer to the Altitude or horizontal and Azimuth or vertical movements of the ETX-80AT telescope. Other terms to describe a telescope's movement may be used with telescopes that have mounts different from the ETX-80AT. Alt/Az Home Position To set your telescope in the "Alt/Az" home position ( Fig. 21). • Loosen the telescope's vertical lock (13, Fig. 1). • Level the optical tube with the horizon. Move the optical tube until the pointer points at approximately "0" on the setting circle. • Tighten the vertical lock to a "firm feel" only. • Unlock the horizontal lock (14, Fig. 1) and turn the telescope horizontally until it points North. Re-lock the horizontal lock. • Remove the 45° prism and eyepiece from the rear cell port. It may interfere with the alignment procedure. After alignment, you may replace the prism and eyepiece. • Press ENTER. 28