Celestron PowerSeeker 21008 Instruction Manual page 22

Aligning the Primary Mirror
Now adjust the primary mirror screws to re-center the reflection of the small secondary mirror, so it's silhouetted against
the view of the primary. As you look into the focuser, silhouettes of the mirrors should look concentric. Repeat steps one
and two until you have achieved this.
Remove the collimating cap and look into the focuser, where you should see the reflection of your eye in the secondary
mirror.
Newtonian collimation views as seen through the focuser using the collimation cap
Secondary mirror needs adjustment.
Both mirrors aligned with the collimating
cap in the focuser
Night Time Star Collimating
After successfully completing daytime collimation, night time star collimation can be done by closely adjusting the
primary mirror while the telescope tube is on its mount and pointing at a bright star. The telescope should be set up at
night and a star's image should be studied at medium to high power (30-60 power per inch of aperture). If a non-
symmetrical focus pattern is present, then it may be possible to correct this by re-collimating only the primary mirror.
Procedure (Please read this section completely before beginning
To star collimate in the Northern Hemisphere, point at a stationary star like the North Star (Polaris). It can be found in the
north sky, at a distance above the horizon equal to your latitude. It's also the end star in the handle of the Little Dipper.
Polaris is not the brightest star in the sky and may even appear dim, depending upon your sky conditions. For the Southern
Hemisphere, point at Sigma Octantis.
Prior to re-collimating the primary mirror, locate the collimation screws on the rear of the telescope tube. The rear cell
(shown in Figure 7-1) has three large screws which are used for collimation and three small screws which are used to lock
the mirror in place. The collimation screws tilt the primary mirror. You will start by loosening the small locking screws a
few turns each. Normally, motions on the order of an
being the maximum required for the large collimation screws. Turn one collimation screw at a time and with a collimation
tool or eyepiece see how the collimation is affected (see the following paragraph below). It will take some experimenting
but you will eventually get the centering you desire.
It is best to use the optional collimation tool or collimating eyepiece. Look into the focuser and notice if the secondary
reflection has moved closer to the center of the primary mirror.
Primary mirror needs adjustment.
Secondary
Mirror
Primary
Mirror
Both mirrors aligned with your eye
looking into the focuser
Mirror Clip
):
1
/ turn will make a difference, with approximately a
8
22
Figure 7-1 PowerSeeker 76AZ
1 3
/ to / turn
2 4