National Geographic NG90EQ owner manual The Equatorial Mount

Complete the following settings in daylight:

1)Insert the 25-mm eyepiece into the eyepiece holder. Look at an easily recognizable, stationary object that is at least 500 feet away. Slightly loosen all locking knobs and move the telescope until the object is in the center of the field of view. Then bring the image into focus.

2)Firmly retighten the locking knobs so that the telescope is locked in position.

3)Look through the finder scope. If the object is not visible or centered in the finder scope, simply release one of the three small adjusting screws holding the finder scope and reposition the finder scope until the object is centered within the X-shaped crosshairs. If the image seen through the finder scope is not clear, turn the eyepiece of the finder scope until the image comes into sharp focus.

4)All screws should be completely tightened as soon as the view through the finder scope coincides with the view of the main telescope.

5)This procedure may need to be repeated to ensure a perfect alignment.

THE EQUATORIAL MOUNT

Your telescope is equipped with an advanced equatorial mount. This type of mount moves the main optical tube in a circular fashion. This is very important because it means that you can set up the NG90EQ to conveniently compensate for the rotation of the Earth.

When you observe an astronomical subject through a telescope it will appear to move across the viewing area. At medium-power magnifications the image can appear to move across the whole viewing area in about 30 seconds. With a simple mounting system, called an altazimuth mount, it can be difficult and frustrating to track an object and keep it in view. The equatorial mount simplifies this operation, but it must be correctly set up.

Pick up and rotate the whole telescope until the front of the main optical unit is facing north. Look fairly high in the sky until you see the familiar star grouping called the Big Dipper. By following an imaginary line up from the two end stars of the dipper (the “pointers”), you will come to a single star with no other stars close by. This is Polaris, or the North Star. Loosen the altitude adjustment knob (See Fig. 21) and raise or lower the angle of the telescope until you can see Polaris centered in the finder scope. Be certain that your finder scope is properly aligned.

Declination knob

(Fig. 21.)

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