Starlight Instruments Feather Touch Micro Focuser for Celestron C9.25 SCT

10:1 Fine-Focus Control for Celestron C9.25 SCTs

This Micro Focuser is known to fit the Celestron C-9.25inch Schmidt-Cassegrain, in its flat-back version. It gives two speeds: a black coarse-focus knob and a gold fine-focus knob at a 10:1 ratio.

This ratio means that ten turns of the fine-focus knob equal one turn of the coarse knob, so you can make small focus changes at the eyepiece or camera. That matters most on nights of good seeing, when high magnification is usable.

How It Works

The Feather Touch Micro Focuser does not change the C9.25's internal focusing method; it still moves the primary mirror by turning the telescope's focus rod. The installation removes the stock brass shaft and bearing assembly, fits an adapter plate to the rear cell and threads the Micro Focuser onto the focus rod, which pushes and pulls on the mirror cell. Ultra-smooth coarse and fine knobs and an ultra-low backlash system are among the Feather Touch standard features.

So the Micro Focuser upgrades the control of the mirror focus, not the way the telescope focuses. Image shift from the moving mirror is not removed; what you gain is fine focus without the coarse jumps of the stock knob.

The Critical Focus Zone

A Schmidt-Cassegrain's long focal length makes the critical focus zone (CFZ), the small range where the image is sharp, very narrow. Outside this zone, details blur and contrast drops, especially on small targets like planetary cloud bands or the components of a tight double star.

The stock focuser's coarse movement makes it easy to move completely through this narrow zone without ever landing in it. The 10:1 fine knob of the Feather Touch lets you move slowly into the CFZ, whether you are observing or imaging.

Two Versions for the C9.25: Check Your Rear Cell

If your telescope is less than a few years old, the style of the back cell shows which version you need. This product is the standard "C" version.

• Standard "C" Version (this product): for a telescope with a flat back.
• "CPC" Version (Sold Separately): If your telescope's rear cell has a distinct triangular pattern cast into the metal, you need the "CPC" version of the Micro Focuser (model FTM-CPC9.25). That version is a separate product.

Check the back of your telescope before ordering, and contact us if you are unsure.

Installation in Nine Steps

You need a Phillips screwdriver and the included 7/64" hex wrench. Position the optical tube horizontally before removing the original focus assembly, or the primary mirror could move; on a German equatorial mount, remove the scope from the mount.

Pull off the rubber knob, remove the four screws of the rectangular outer cover plate (keep them), turn the brass shaft clockwise to bring the mirror back and remove the small Phillips screw at the end of the focus rod. Remove the three screws of the recessed focus assembly cover plate (a knife blade or flat screwdriver helps lift it), then turn the brass shaft counterclockwise, quite a few turns, to remove the bearing assembly. Attach the adapter plate with the original four screws, beveled side toward the telescope and large hole on the left. Thread the Micro Focuser onto the focus rod, push it the last 1/4", and attach it with the three included hex-head screws.

What Comes With It

Apart from a Phillips screwdriver, the parts and wrench for the installation come with the focuser:

• Feather Touch SCT Micro Focuser: The main dual-speed focusing unit.
• Adapter Plate: mounts on the rear cell with the telescope's original four cover plate screws.
• Hex-Head Screws (x3): attach the Micro Focuser to the telescope.
• 7/64" Hex-Head Wrench.

Motorizing Your Focuser with the HSM20 Stepper Motor

The Handy Stepper Motor (HSM20), sold separately, fits any Feather Touch Micro Focuser.

Separate HSM installation instructions are available for the Micro Focuser. The motor runs on a Focuser Boss II or EFS controller, which connects to ASCOM software on your PC and offers temperature compensation using the motor's built-in thermistor.

USA-Made Build and Materials

Starlight Instruments designs, machines, anodizes and assembles its Feather Touch components in-house in the USA. The brochure lists durable hardened stainless steel, steel and aluminum construction among the Feather Touch standard features.

The fine focus knob is anodized aluminum.