Installation Instructions – Celestron 8” Telescopes
Note: The SCT MicroFocuser is designed to work on most Celestron SchmidtCassegrain telescopes (SCTs). Newer model SCTs use a stop on the baffle tube toprevent the mirror from sliding off the baffle tube. Older scopes use a C-clip on the focus
shaft to hold the mirror in place. Removing this clip is necessary for the installation ofthe MicroFocuser, so some older scopes will not be able to use the MicroFocuser.
During the assembly instruction you will be shown how to test an older telescope to seewhether it will work with the SCT MicroFocuser.

Important:

The telescope optical tube must be positioned horizontally before
removing the original focus assembly. If the telescope is not horizontal the primary
mirror could move during the installation.
Required Tools:

Phillips Screwdriver (some models)
1/16” Hex-Head Wrench (some models)
7/64” Hex-Head Wrench (included)

Step 1 Remove Focus Knob

The newest Celestron telescopes have a rubber knob which can be pulled off. Older 8"telescopes will have a metal focus knob which must be removed using a 1/16” hex-headwrench to loosen a small set screw. Once the knob is removed you will see the brassfocus shaft as shown in the second picture above.

Step 2 Remove Focus Assembly Cover

There are 3 small screws which hold the focus assembly cover in place. These will be
Phillips-head screws on newer scopes, but some models will have hex-head screws.
Remove these screws and take off the flat cover plate, exposing the inside of the focus
assembly.

Step 3Move Mirror Back to Expose C-Clip or Screw

Rotate the brass portion of the focus assembly clockwise. This will bring the mirror backand expose the threaded portion of the focus shaft. At the tip of this threaded bolt will beeither a small C-clip or a screw which will be removed in the next step.

Step 4 Remove C-Clip or Screw

The C-clip at the end of the focus shaft must be removed to install the SCT MicroFocuser. The clip should be removable by hand, but you may use needle-nose pliers or asimilar tool if necessary. Be careful not to scar the threads of the focus shaft as the SCT
MicroFocuser must be threaded on in a later step. If your telescope has a screw, simply
remove this with a screwdriver.

Step 5 Remove Focus Bearing Assembly

Rotate the brass portion of the focus shaft counterclockwise. This will unthread the brass
shaft and bearing assembly from the threaded rod. Remove these parts entirely (you willturn the brass shaft quite a few times to remove it).

Note: If you have an older scope, please test it at this point to see if there is a stop on thebaffle tube. If not, you will not be able to use the SCT MicroFocuser on your telescope.
If you have a new telescope (year 2000 or later), please skip ahead to Step 7.

Step 6 Test for Baffle Tube Stop

Carefully push the threaded focus shaft forward (moving the entire mirror assembly). Do
not push the shaft all the way into the telescope. If there is a baffle stop on yourtelescope you will only be able to push the mirror forward until the threaded shaft is justflush with the back of the telescope (see picture on right). If you can push the mirror
beyond this, you do not have a baffle stop and it is possible that the mirror could fall off
the baffle tube. Normally the C-clip or screw prevents this, but the SCT MicroFocuser
will not work with the clip in place.

Step 7 Attach the SCT MicroFocuser

Use the three provided hex-head screws and wrench to attach the SCT MicroFocuser tothe telescope. You are now ready to head out under the stars! Use the black knob forcoarse focus and the brass knob for fine focus (10:1 ratio).