Advanced Features

	North
Declination	Pointer
at 0˚

Fig. 25: Alt/Az Home Position.

Terrestrial Observing

The ETX-80AT-BB makes an excellent high-resolution, terrestrial (land) telescope. Viewing ter- restrial 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 eye- piece, magnify these heat waves less than higher power eyepieces. Therefore, low power eye- pieces 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 bet- ter 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, limit- ed 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 19.

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 align- ment stars. The database displays after One-Star Alt/Az or Two-Star Alt/Az Alignment is select- ed. .

The term "Alt/Az." is frequently used to refer to the Altitude or horizontal and Azimuth or verti- cal movements of the ETX-80AT-BB telescope. Other terms to describe a telescope's move- ment may be used with telescopes that have mounts different from the ETX-80AT-BB.

Alt/Az Home Position

To set your telescope in the "Alt/Az" home position (also see Fig. 20, page 19).:

•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 “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.