National Geographic NG90EQ Quick start guide

NG90EQ

Maksutov-Cassegrain

Telescope

Instructions

and

Owner’s Manual

A. Equatorial mount G. 3X Barlow lens M. Accessory tray

screws

a. Counterweight H. Main optical unit N. Tripod leg

bolts

B. Counterweight shaft I. Accessory tray O. Tripod Legs

C. Slow-motion control knobs J. Finder scope

D. 9mm eyepiece K. 45º Diagonal prism

E. 25mm eyepiece L. Mounting plate

WARNING!

NEVER aim your telescope at the sun or even close to the sun!

Instant and irreversible damage can occur,

including blindness!

Do not let children use any telescope without adult supervision.

A B CD E F

H I J K

Parts of your NG90EQ Telescope:

A. Equatorial mount

B. Counterweight shaft

C. Counterweight

D. Slow-motion control knobs (2)

E. 9-mm eyepiece

F. 25-mm eyepiece

G. 3X Barlow lens

H. Main optical unit

I. Accessory tray

J. Finder scope

K. 45º prism

L. Mounting plate

M. Accessory tray screws (3)

N. Tripod bolts (3)

O. Tripod legs (3)

Introduction

Congratulations on your purchase of a precision-crafted NATIONAL GEOGRAPHIC™

telescope. With proper care and handling of your telescope, you will enjoy the pleasure

of looking at nature’s wondrous sights through the eye of this instrument for many

years.

The NG90EQ has been designed to provide views of the moon’s craters, Jupiter’s major

moons, and Saturn’s rings, in addition to dozens of galaxies, star clusters, and nebulae.

As a terrestrial (land) telescope, the NG90EQ delivers great views of mountains,

valleys, and many other features of the world around us. You can also use the NG90EQ

to study animals and landscapes at a distance. To obtain the best performance from

your telescope, please read this manual carefully and completely.

WARNING!

CHOKING HAZARD

Small parts. Not suitable for

children under 3 years.

ASSEMBLY

1) Carefully remove all parts from the cardboard cartons and lay them on a table or

on the floor in order to take an inventory of all the pieces. Keep your box for storage

or in case you ever need to ship your telescope.

2) Each aluminum tripod leg can extend to almost double its closed length. This

enables the height of the telescope to be adjusted to comfortably suit most users.

Each leg is equipped with a locking knob that can be loosened to perform this

adjustment and then retightened. These locking knobs may already be attached to

the tripod legs, or they may be packaged in a small plastic bag. If they are already

attached you can extend the tripod legs to the desired height and then tighten these

knobs. If they are separately packaged you will have to first insert them into the

threaded holes located on the side of the black collar near the bottom of each closed

tripod leg.

3) The tripod legs now need to be attached to the equatorial mount. The top of each

leg is attached with a tripod bolt passed through the holes at the top of each leg.

Position one of the three arms of the equatorial mount so that it fits between the leg

sections. Insert a bolt through the first tripod section, then through the equatorial

mount arm, and finally through the second leg section (See Fig. 1). You will note that

one of the leg sections has a hexagonal (8-sided) hole. This is the side from which

you insert the bolt. When the bolt comes out the other side, place a round washer

and a then a wing nut over the bolt. Tighten the wing nut firmly. NOTE: Each tripod

leg has a black metal flap about halfway down its length. This is a bracket to

hold the accessory tray and must it be located on the inward-facing side of the

tripod leg.

(Fig. 1)

4) Attach the accessory tray to the tripod by inserting an accessory tray screw

downward through each of the three small holes located near the edge of the

accessory tray. Lift up the black metal accessory tray bracket on one tripod leg so

that it is at a right angle to the leg. Push the accessory tray screw through the

accessory tray and then through the slot in the accessory tray bracket. Place a

washer then a wing nut over the screw and tighten the wing nut finger tight (See Fig.

2). Repeat this procedure for the other two accessory tray brackets (See Fig. 3).

(Fig. 2) (Fig. 3)

5) The main optical unit is attached to the equatorial mount with a black cast metal

mounting plate. This mounting plate has four chromed screws mounted in it. Remove

all four screws. The mounting plate has one smooth face and one face with small

ridges. Place the smooth face against the underside of the main optical unit. Then

insert the two slotted chromed screws through the inner holes so that they engage

with the two threaded holes on the underside of the main optical unit. Tighten these

with a screwdriver (See Fig. 4).

(Fig. 4)

6) Position the main optical unit, with the mounting plate attached, over the equatorial

mount as shown in Fig. 5. Insert the two chromed screws with the Phillips (+) heads into

the two holes in the equatorial mount so that they engage the two holes at the ends of

the mounting plate. Tighten with a screwdriver (See Fig. 6 and Fig. 7).

(Fig. 5) (Fig. 6) (Fig. 7)

7) The counterweight balances your telescope and makes it easy to adjust and

position. Hold the counterweight in your hand so you can see through the hole in the

weight. Make sure that the black tightening knob on the counterweight is facing

down. When you look through the counterweight, if you see that the hole is blocked

by a metal rod, slowly turn the tightening knob counterclockwise to loosen it until you

see that the hole is clear (see Fig. 8). Then insert the counterweight shaft through the

counterweight. Turn the tightening knob clockwise to tighten it. Then insert the

threaded end of the counterweight rod into the equatorial mount and turn it clockwise

until it stops (See Fig. 9 and Fig. 10).

(Fig. 8) (Fig. 9) (Fig. 10)

8) Attach the long slow-motion control knob to the chrome right ascension shaft as

shown in Fig. 11. Tighten the small chrome knob on the slow-motion control until it is

tight against the flat side of the right ascension shaft. Attach the shorter slow-motion

control to the chrome declination shaft as shown in Fig. 12 and tighten it into position.

Fig. 13 shows the completed assembly.

(Fig. 11) (Fig. 12) (Fig. 13)

9) Slide the finder scope into its bracket on top of the main optical unit. Tighten the

two small chrome screws to hold it securely in position (See Fig. 14).

(Fig. 14)

10) Remove the plastic dust cap from the upper eyepiece port and insert the 25-mm

eyepiece into the eyepiece holder. Tighten the small set screw to hold the eyepiece

securely in place. (See Fig. 15).

(Fig. 15)

11) Remove the plastic dust cap from the rear eyepiece port and attach the 45º

diagonal prism by turning its collar clockwise over the threaded piece on the back of

the main optical unit (See Fig. 16 and Fig. 17).

(Fig. 16) (Fig. 17)

FINDER SCOPE ALIGNMENT

Since a telescope has a narrow field of view by design, it can be challenging to locate a

particular star or planet. For this reason the telescope is fitted with a low-power, wide-

field miniature telescope called a finder scope. Always use your finder scope to locate

the object you want to view FIRST. The finder scope should be aligned with the

main telescope tube before you begin using the telescope, in order that both

scopes are positioned to always provide exactly the same angle and view.

Note: Objects in the finder scope are upside down. This is normal and is common to all

astronomical telescopes.

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.)

You can also adjust the declination by raising or lowering the angle of the main optical

unit until the arrow on the degree scale located on the side of the equatorial mount

points toward the north latitude of your observing location. If you do not know your

viewing position’s north latitude, you can call a local weather office or airport to find out.

Use your finder scope to locate an object. Focus on the object and begin observing. As

you notice the viewed object move across the viewing area slowly turn the slow-motion

cable extending from the left side of the telescope until the object is centered again. If

your setup was not accurate you will notice that the subject is moving very slowly either

up or down. A slight turn of the declination slow-motion control knob extending from the

back of the telescope will counteract this slight error (See Fig. 22).

(Fig. 22)

A WORD ABOUT THE TWO EYEPIECE PORTS

The NG90EQ is fitted with two eyepiece ports. The top port generally is used for

astronomical viewing. The view you see will be right side up, but will be laterally

reversed, like looking in a mirror. This is normal, and is of no consequence.

The rear port, with the 45º diagonal prism attached, is normally used for terrestrial, or

land viewing. When an eyepiece is placed in the 45º diagonal prism the view is correctly

oriented, like looking through a pair of binoculars, though with much higher magnifying

ability.

The image produced by the telescope can be directed to one port or the other with the

flip mirror on the main optical unit. In Fig. 18 the image is being directed to the upper

eyepiece port. In Fig. 19 it is being directed to the rear optical port.

(Fig. 18) (Fig. 19)

The two eyepiece ports can be used in another way. With an optional camera adapter

and appropriate T-ring a 35-mm SLR camera body can be attached to the rear eyepiece

port. The 45º diagonal prism must first be removed. With an eyepiece in the top

eyepiece port and a camera body attached to the rear eyepiece port a subject can be

observed with the eyepiece. Then by simply adjusting the flip mirror, a picture can be

taken through the rear eyepiece port.

FOCUSING FOR ALL VIEWING IS ACCOMPLISHED BY SLOWLY TURNING THE

RUBBERIZED WHEEL LOCATED AT THE RIGHT REAR OF THE MAIN OPTICAL

UNIT. IF THE IMAGE SEEN IN THE EYEPIECE IS IN FOCUS, THE IMAGE SEEN BY

THE CAMERA WILL ALSO BE IN FOCUS.

ABOUT MAGNIFICATION

The magnification power of a telescope indicates how much an image is enlarged or

how big and close it appears to the viewer. The focal length of the eyepiece, combined

with the focal length of the telescope, determines the magnification power. To calculate

the power of your telescope with any particular eyepiece, simply divide the focal length

of the telescope (1,200 mm) by the focal length of the eyepiece (indicated in “mm” on

the eyepiece collar).

Example: 1200-mm focal length (tube) = 48X magnification power

25-mm focal length (eyepiece)

The following magnification values are achieved when using the Barlow lens and the

interchangeable eyepieces:

Eyepiece Power Power With 3X Barlow Lens

25 mm 48X 144X

9 mm 133X 400X

Higher magnification powers can be achieved by using the included 3X Barlow lens.

The 3X Barlow lens is inserted between the telescope and the eyepiece. In Fig. 20 it is

shown being used at the rear eyepiece port. It can be used at either eyepiece port.

(Fig. 20)

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