Orion XT4.5 instruction manual Assembly of the Dobsonian base, Installing the Eyepiece Rack

2. Assembly

Now that you have unpacked the boxes and familiarized yourself with all the parts in front of you, it's time to begin assembly. The optics of the telescope are already installed in the tube, so most of the required assembly concerns the Dobsonian base.

Assembly of the Dobsonian base

Refer to Figure 2 during base assembly. The base need only be assembled once. The assembly process takes about 30 minutes and requires a Phillips screwdriver, and an adjustable crescent wrench. When tightening screws, tighten them until firm, but be careful not to strip the holes by over- tightening. Children under the age of 12 should work with an adult.

C

C

B

L

I

H

E

D

A K

F

G

Figure 2. Exploded view of the Dobsonian base.

1.Screw the plastic feet into the underside of the ground baseplate (A) using the self-tapping wood screws provided, with a Phillips screwdriver. Insert the screws through the feet and thread them into the predrilled starter holes.

2.Loosely attach the front brace (B) to the two side panels (C) with four of the base assembly screws in the predrilled holes. The side panels should be oriented so the SkyQuest labels are facing outward. Do not completely tighten the screws yet.

3.Attach the two sides (C) with the front brace attached to the

top baseplate (D) with the remaining six base assembly screws in the predrilled holes. Tighten all six screws.

4.Tighten the four side screws installed earlier. Press a trim cap onto the heads of each of these screws.

5.Insert the white nylon bushing (E) into the hole in the cen- ter of the top baseplate (D). Tap the nylon bushing in so it goes all the way into the top baseplate. The nylon bushing should be flush with the top surface of the top baseplate.

6.Insert the T-nut (K) into the center hole of the ground base- plate (A) so the nut’s flanged top is on the same side of the baseplate as the Teflon pads. Thread the large hex-head bolt (G) with a 3/8" washer (F) attached up through the ground baseplate and through the T-nut until it is tight.

7.Now position the top baseplate (D) (with side panels attached) over the ground baseplate and lower it so the bolt goes through the nylon spacer in the center hole of the top baseplate. Now thread the remaining 3/8" washer (H) and lock nut (I) onto the bolt’s shaft. You might need to hold the bolt's head in place with another crescent wrench or pliers. Tighten the lock nut with the wrench just enough to allow a slight separation of the top and bottom baseplates when the mount is lifted. The purpose of the lock nut is merely to keep the two baseplates from coming apart when moving the tel- escope. Over-tightening the lock nut (I) will make the mount difficult to rotate in the azimuthal (horizontal) direction.

8.The rubber bumper (L) provides a convenient “stop” for the telescope’s altitude motion; it prevents the telescope mirror cell from being knocked against the hard surface of the base’s front brace. At the bottom of the interior surface of the front brace, you will notice a small index mark engraved. Remove the backing from the rubber bumper and position the bumper over the index mark, as shown in Figure 3. Press firmly so the adhesive holds the bumper securely in place.

Figure 3. Position the rubber bumper “stop” over the index mark on the inside surface of the front brace.

Installing the Eyepiece Rack

The aluminum eyepiece rack holds three 1.25" eyepieces in a convenient place on the base, within easy reach while you're observing. A 1.25" barlow can also be held in the rack.

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