Orion SKYQUEST XT6 User Manual download pdf (Page 11)

Aligning the Secondary Mirror

With the collimation cap in place, look through the hole in the

cap at the secondary (diagonal) mirror. Ignore the reflections

for the time being. The secondary mirror itself should be cen-

tered in the focuser drawtube, in the direction parallel to the

length of the telescope. If it isn’t, as in Figure 12b, it must be

adjusted. This adjustment will rarely, if ever, need to be done.

It helps to adjust the secondary mirror in a brightly lit room

with the telescope pointed toward a bright surface, such as

white paper or wall. Placing a piece of white paper in the tele-

scope tube opposite the focuser (i.e., on the other side of the

secondary mirror) will also be helpful in collimating the sec-

ondary mirror. Using a 2mm hex key, loosen the three small

alignment set screws in the center hub of the 4-vaned spider

several turns. Now hold the mirror holder stationary (be care-

ful not to touch the surface of the mirrors), while turning the

center screw with a Phillips head screwdriver (see Figure 13).

Turning the screw clockwise will move the secondary mirror

toward the front opening of the optical tube, while turning the

screw counter-clockwise will move the secondary mirror

toward the primary mirror.

Note: When making these adjustments, be careful not to

stress the spider vanes or they may bend.

When the secondary mirror is centered in the focuser draw-

tube, rotate the secondary mirror holder until the reflection of

the primary mirror is as centered in the secondary mirror as

possible. It may not be perfectly centered, but that is OK. Now

tighten the three small alignment screws equally to secure the

secondary mirror in that position. If the entire primary mirror

reflection is not visible in the secondary mirror, as in Figure

12c, you will need to adjust the tilt of the secondary mirror.

This is done by alternately loosening one of the three align-

ment setscrews while tightening the other two, as depicted in

Figure 14.The goal is to center the primary mirror reflection in

the secondary mirror, as in Figure 12d. Don’t worry that the

reflection of the secondary mirror (the smallest circle, with the

collimation cap “dot” in the center) is off-center.You will fix that

in the next step.

Adjusting the Primary Mirror

The final adjustment is made to the primary mirror. It will need

adjustment if, as in Figure 12d, the secondary mirror is cen-

tered under the focuser and the reflection of the primary

mirror is centered in the secondary mirror, but the small reflec-

tion of the secondary mirror (with the “dot” of the collimation

cap) is off-center.

The tilt of the primary mirror is adjusted with three spring-

loaded collimation thumbscrews on the back end of the optical

tube (bottom of the primary mirror cell); these are the larger

thumbscrews. The other three smaller thumbscrews lock the

mirror’s position in place; these thumbscrews must be loos-

ened before any collimation adjustments can be made to the

primary mirror.

To start, turn the smaller thumbscrews a few turns each

(Figure 15). Use a screwdriver in the slots, if necessary.

Now, try tightening or loosening one of the larger collimation

thumbscrews with your fingers (Figure 16). Look into the

focuser and see if the secondary mirror reflection has moved

closer to the center of the 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 far-

ther away from the ring on the center of the primary mirror.

Figure 13. To center the secondary mirror under the focuser,

hold the secondary mirror holder in place with one hand while

adjusting the center bolt with a Phillips screwdriver. Do not touch the

mirror’s surface!

Figure 14. Adjust the tilt of the secondary mirror by loosening or

tightening the three alignment set screws with a 2mm hex key.

Figure 15. The three small thumbscrews that lock the primary

mirror in place must first be loosened before any adjustments can

be made.

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Orion SKYQUEST XT6 User Manual Page 11

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