Starlight Instruments Feather Touch Micro for Celestron C11 SCT (NOT CPC1100)

A Precision Focuser for Celestron's 11" Flat-Back SCTs

This Feather Touch Micro Focuser replaces the original focus knob and bearing assembly of the Celestron C-11 and threads onto the telescope's own focus rod, which pushes and pulls on the mirror cell.

The FTM-C11 is the standard "C" version, for a C-11 with a flat back; it is not for the CPC1100. Starlight's instructions cover older 11" telescopes with a metal focus knob and the NexStar 11 GPS with a rubber knob.

Dual-Speed 10:1 Focusing

The Micro Focuser gives two focusing speeds: the black knob for coarse focus and the smaller gold fine knob at a 10:1 ratio, so ten turns of the fine knob equal one turn of the coarse knob. An ultra-low backlash system is among the Feather Touch standard features.

The fine knob makes small, deliberate adjustments of the primary mirror much easier, for visual work and imaging alike.

Why Fine Focus Matters on a Schmidt-Cassegrain

A C-11's long focal length makes the critical focus zone, the range where the image is sharp, very shallow. With the stock focuser, it's easy to move the mirror straight through this narrow zone, never quite landing on the sharpest possible image. This is especially true when viewing planets at high power or trying to capture fine detail in CCD images.

The 10:1 fine knob lets you approach focus slowly, which helps on planetary detail, close double stars and camera focus.

Compatibility Check: Is Your C11 a Flat-Back Model?

If your telescope is less than a few years old, the back cell shows which version you need. This FTM-C11 is the standard "C" version for a flat back. A triangular pattern on the back needs the "CPC" version of the Micro Focuser (sold separately).

• Flat back: this model.
• Triangular pattern on the back: the CPC version; this model is not for the CPC1100.

Installation in Seven Steps

Position the optical tube horizontally before removing the original focus assembly, or the primary mirror could move.

Remove the focus knob, turn the brass shaft clockwise to bring the mirror back and remove the small Phillips screw from the end of the focus rod. Remove the three cover plate screws (keep them) and the plate, then turn the brass shaft counterclockwise, quite a few turns, to remove the bearing assembly. Thread the Micro Focuser onto the focus rod and push it the last 1/4" in, which takes up some of the focus change and makes it quicker to find focus the first time. Attach it with the three original Phillips screws.

Tools for Installation

The package contains the Feather Touch Micro Focuser, and it attaches with your telescope's original screws. You will need these tools:

• Phillips Screwdriver: Required for all compatible models to remove the cover plate screws.
• 1/16” Hex-Head Wrench: Only required for older C11s that have a metal focus knob secured by a small set screw. Not needed for NexStar 11 GPS models with a rubber pull-off knob.

Motorizing Your FTM-C11 with the HSM20 Stepper Motor

The Handy Stepper Motor (HSM20), sold separately, fits any Feather Touch Micro Focuser, for computer-controlled focusing.

With a Focuser Boss II or EFS controller, the HSM20 lets ASCOM software focus without you touching the telescope, and the controllers offer temperature compensation using the motor's built-in thermistor.

Starlight Instruments Build: Designed and Machined in the USA

Starlight Instruments designs, machines, anodizes and assembles its Feather Touch components in-house in Columbia City, Indiana.

The brochure lists durable hardened stainless steel, steel and aluminum construction and an anodized aluminum fine focus knob among the Feather Touch standard features.