Starlight Instruments SCT MicroFocuser Installation Instructions – Celestron 91 /4” Telescopes [EN]

Installation Instructions – Celestron 91/4” Telescopes

Important:

removing the original focus assembly. If the telescope is not horizontal the primary
mirror could move during the installation. If you have a German equatorial mount, it is
recommended that you remove the scope from the mount for this installation.

Required Tools: Phillips Screwdriver
7/64” Hex-Head Wrench (included)

The telescope optical tube must be positioned horizontally before

Step 1

Remove Focus Knob

Begin by pulling off the rubber focus knob exposing the brass shaft underneath, as shown
above.

Step 2

Remove the 4 screws holding on the rectangular outer cover plate. Keep these screws as
they will be used later to attach the new MicroFocuser adapter plate.

Remove Outer Cover Plate

Step 3

Turn the brass focus shaft clockwise to bring the mirror back and expose the Phillips­head screw at the end of the threaded focus rod.

Move Primary Mirror Back

Step 4

Use screwdriver to remove the small Phillips screw from the end of the threaded focus
rod.

Remove Set Screw

Step 5

Use screwdriver to remove three screws from the focus assembly cover plate (the three
screws around the outside of the focus shaft). Remove the cover plate. This can be
tricky due to the plate being recessed. A knife blade or flat screwdriver can be helpful.

Remove Focus Assembly Cover Plate

Step 6

Turn the brass focus shaft counterclockwise to remove it from the threaded focus rod.
This will take quite a few turns. Once the bearing assembly is removed, only the
threaded focus rod (which pushes and pulls on the mirror cell to focus the telescope) will
be left sticking out of the telescope as above.

Remove Focus Bearing Assembly

Step 7

Install Adapter Plate

Use the original 4 screws to attach the included adapter plate. Be sure the beveled side is
in toward the telescope. There is only one proper orientation for the plate, with the large
hole on the left side.

Step 8

Begin threading the SCT MicroFocuser onto the threaded focus rod. When there is only
about 1/4" left to go, simply push the focuser the rest of the way in. This will take up
some of the focus travel from when you removed the original focuser, making it quicker
to return to the proper focus the first time you use your telescope after the SCT
MicroFocuser installation.

Thread on SCT MicroFocuser

Step 9

Use the three included hex-head screws to attach the SCT MicroFocuser to the telescope.
You are now ready to head out under the stars!

Attach the SCT Micro Focuser