Starlight Instruments Feather Touch Micro for Celestron C8 (NOT CPC/NexStar SE)

A 10:1 Focusing Upgrade for the Celestron C8

The Feather Touch Micro has a black knob for coarse focus and a brass knob for fine focus at a 10:1 ratio: ten turns of the fine knob equal one turn of the coarse knob, so small adjustments near focus are much easier.

At the long focal lengths of a Schmidt-Cassegrain, the depth of the critical focus zone is incredibly shallow. A single-speed knob moves the mirror a long way for a small turn, so it is easy to go past best focus. The Feather Touch Micro replaces the knob and bearing assembly on the telescope's focus shaft, giving you finer control of the primary mirror's position.

• Rear port unchanged: the Micro Focuser sits on the focus shaft beside the rear port, not in the light path, so it adds nothing to the length of your image train.
• High magnification: on planets and close double stars, the 10:1 fine knob makes the small adjustments of final focus easier.
• Smooth: Feather Touch standard features include ultra-smooth coarse and fine knobs and an ultra-low backlash system.

Compatibility Check: Is Your C8 a Flat-Back Model?

The FTM-C8 is known to fit the Celestron C-8 SCT, not the CPC or NexStar SE. If your telescope is less than a few years old, the back cell shows the version: this is the standard "C" version, for a flat back.

If your C8 has a triangular pattern cast into the rear cell, you will need the "CPC" version of the Micro Focuser, not this model. Some older C8s also cannot take the Micro Focuser, and the instructions show how to test for this.

• Older Scope Exclusion: The upgrade requires removing the C-clip or screw from the end of the focus shaft. On some older C8s, this clip was the only component preventing the primary mirror from sliding off the baffle tube. Newer scopes have a stop on the baffle tube. The instructions show how to test an older scope for the stop before attaching the Micro Focuser; a telescope from 2000 or later skips the test.
• Correct Model is Key: Ordering the correct version for your telescope's rear cell style (flat vs. triangular) is essential for a successful installation.

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 (rubber knobs pull off; older metal knobs have a set screw) and the three screws of the focus assembly cover (Phillips on newer scopes, hex-head on some models). Turn the brass part clockwise to bring the mirror back, remove the C-clip (by hand or with needle-nose pliers, without scarring the threads) or the screw, then turn the brass part counterclockwise, quite a few turns, to remove the bearing assembly. On an older scope, carefully push the focus shaft forward: with a baffle stop the shaft only goes flush with the back of the telescope; if it goes further, there is no stop and the Micro Focuser cannot be used. Attach the Micro Focuser with the three provided hex-head screws and wrench.

• Tools You Will Need: Depending on your C8 model, you may need a Phillips screwdriver and a 1/16” hex-head wrench in addition to the 7/64” hex-head wrench that comes with the focuser.
• Horizontal Tube Position: This is a mandatory step. If the tube is tilted, the primary mirror can move on the baffle tube once the stock focuser assembly is removed.

Motorizing with the HSM20

The Handy Stepper Motor (HSM20), sold separately, fits any Feather Touch Micro Focuser, for electronic focusing from a computer or controller.

The HSM20 is run by the Starlight Instruments Focuser Boss II or Electronic Focusing System (EFS), which connect to ASCOM software and offer temperature compensation using the motor's built-in thermistor. Separate HSM installation instructions are available for the Micro Focuser.

Made in the USA: Starlight Instruments Build Quality

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.