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4. Collimation

Collimation is the process of adjusting the mirrors so they are 
correctly aligned with one another. Your telescope’s optics 
were aligned at the factory, but they could become misaligned 
during shipment. Accurate mirror alignment is important to 
ensure the peak performance of your telescope, so it should 
be checked regularly. Collimation is relatively easy to do and 
can be done in daylight.

The Collimation Cap and Mirror Center Mark

Your XT PLUS comes with a “quick-collimation” cap (

Figure 

21). This is a simple cap that fits on the focuser drawtube like a 

dust cap, but has a hole in the center and a reflective material 
on the underside. The cap helps center your eye so that col-

Figure 22. 

The telescope ready for collimation, with the 

tube oriented horizontally, the collimation cap in place on the 

focuser, and a piece of white paper placed inside the tube 

opposite the focuser.

Figure 23. 

Collimating the optics. 

(a) 

When the mirrors are 

properly aligned, the view down the focuser drawtube should 

look like this; 

(b) 

With the collimation cap in place, if the 

optics are out of alignment, the view might look something 

like this; 

(c) 

Here, the secondary mirror is centered under 

the focuser, but it needs to be adjusted (tilted) so that the 

entire primary mirror is visible; 

(d) 

The secondary mirror 

is correctly aligned, but the primary mirror still needs 

adjustment. When the primary mirror is correctly aligned, the 

“dot” will be centered, as in 

(e)

.

a.

b.

c.

d.

e.

Figure 21. 

The quick collimation cap, which features a 

reflective inner surface, helps in centering reflections of the 

optics in the focuser during the collimation process.

Summary of Contents for 8974 XT8 PLUS

Page 1: ...tus Corporate Offices 89 Hangar Way Watsonville CA 95076 USA Providing Exceptional Consumer Optical Products Since 1975 Copyright 2013 2014 Orion Telescopes Binoculars All Rights Reserved No part of t...

Page 2: ...anel Front panel Handle Dobsonian base Top groundplate Bottom groundplate 28mm DeepView eyepiece 2 XT8 and XT10 2 Extension adapter XT8 and XT10 10mm Sirius Pl ssl eyepiece 1 25 25mm Sirius Pl ssl eye...

Page 3: ...diately call Orion Customer Support 800 676 1343 for assistance Parts List Box 1 Optical Tube Assembly and Accessories Qty Description 1 Optical tube assembly 1 Dust cover 1 10mm Sirius Pl ssl eyepiec...

Page 4: ...panel from the outside and thread the bearing cylinder onto it You can tighten the cylinder by hand or if needed with the supplied 4mm hex key Repeat for the remaining three bearing cylinders 4 Attach...

Page 5: ...The latter bushing R is longer than the width of the side panel by 1 4 or so that s by design 13 To install the eyepiece rack S find the two pilot holes on the left side panel and screw one of the woo...

Page 6: ...e knob to thread the bolt into the threaded insert of the tube assembly s right side bearing Thread the bolt until it stops and the knob is lightly tightened 3 On the other altitude axis coupling knob...

Page 7: ...cal objects at night This way you will not have to fum ble around trying to orient yourself in the dark Find a spot outdoors where you have plenty of room to move around the telescope and where you ha...

Page 8: ...ows one to make very tiny focusing increments for ultra precise focusing To focus insert an eyepiece into the focuser and secure it with the thumbscrew s Now slowly rotate one of the coarse focus knob...

Page 9: ...power knob see Figure 11 clockwise until you hear the click indicating that power has been turned on Look through the back of the reflex sight with both eyes open to see the red dot Position your eye...

Page 10: ...through On nights of good seeing the atmosphere will be still and will yield the least amount of dis tortion On nights of poor seeing the atmosphere will be turbu lent which means different densities...

Page 11: ...that permits daytime viewing of our nearest star the Sun Figure 20 The white light filter uses high quality Baader Astro Solar safety film which reduces the transmission of the Sun s radiation to a sa...

Page 12: ...lescope ready for collimation with the tube oriented horizontally the collimation cap in place on the focuser and a piece of white paper placed inside the tube opposite the focuser Figure 23 Collimati...

Page 13: ...secondary mirror and the reflection of the secondary mirror and your eye centered in the reflection of the primary mirror as in Figure 23a If anything is off center as in Figure 23b proceed with the...

Page 14: ...primary You can tell this easily with the collimation cap and mirror center mark by simply watching to see if the dot of the collimation cap is moving closer or farther away from the ring on the cent...

Page 15: ...t Focal Ratio f 5 9 Focuser 2 Crayford dual speed 11 1 accepts 2 eyepieces and 1 25 eyepieces with included adapter Optical tube material Rolled steel Eyepieces 10mm Sirius Pl ssl 1 25 barrel dia 28mm...

Page 16: ...trument has been abused mishandled or modified nor does it apply to normal wear and tear This warranty gives you specific legal rights It is not intended to remove or restrict your other legal rights...

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