Starlight Instruments Handy Stepper Motor w/ Manual Focus Over-Ride

HSM20, HSM30 & HSM35: Fitment Across 3 Focuser Classes

Starlight produces the HSM in three models, each for a group of focusers. Choose the one that matches your focuser.

• HSM20 Fits: any Feather Touch Micro Focuser for SCTs, the Feather Touch retrofit pinion assembly upgrades (MPA retrofits for Takahashi and Tele Vue) and Feather Touch Crayford focusers; the site copy says the 2.0" Feather Touch focusers.
• HSM30 Fits: the 2.0", 2.5" and 3.0" Feather Touch rack and pinion focusers, the TRUE 3.0" Feather Touch, and the 2.7" Astro-Physics focuser with the Feather Touch upgrade.
• HSM35 Fits: any 3.5" Feather Touch focuser, and the Astro-Physics 3.5" and 4.0" focusers with the Feather Touch pinion assembly upgrade.

Up to 24,300 Steps Per Inch for Critical Focus

The HSM30 and HSM35 have 24,300 steps per inch, and the HSM20 19,450 steps per inch. Fine steps let an autofocus routine make small adjustments, which matters most with fast optical systems where the zone of sharp focus is shallow.

With the built-in thermistor, the EFS and Focuser Boss II can use temperature to adjust focus as the night cools; the EFS brochure lists temperature compensation and backlash correction among its features.

Manual Override by Turning the Housing

The core design of the Handy Stepper Motor delivers the precision of automated focusing without sacrificing the immediate, tactile control of manual adjustment. A simple counter-clockwise turn of the motor housing disengages the stepper motor's gears, allowing you to use the focuser's own knobs as you normally would. Turning the housing clockwise re-engages the motor for automated control.

This is useful for initial setup, quick visual checks or whenever the controller is not connected.

Control via 2 Systems: Focuser Boss II and EFS

The HSM is a component that requires a dedicated controller, sold separately. Starlight offers two options: the Focuser Boss II and the Electronic Focusing System (EFS). The EFS comes with an ASCOM driver (ASCOM Platform 6 or later), a hand controller and its own features such as backlash correction and temperature compensation. The Focuser Boss II hub runs one or two focusers over serial, USB or wired Ethernet, with optional WiFi, through an ASCOM Local Server, and Mac users can use TheSky X and Equinox. The motor's built-in thermistor provides temperature control through either controller.

Starlight HSM vs. PDMS: A 2-Motor System Comparison

Starlight Instruments offers two motor systems for its focusers, the direct-drive HSM and the belt-driven Posi Drive Motor System (PDMS). Starlight offers the PDMS for heavier image trains and for non Feather Touch focusers, stating it can lift in excess of 56 pounds.

• Handy Stepper Motor (HSM): A compact, all-in-one unit that clamps directly onto the focuser's pinion assembly. Turning the housing disengages the gears for manual focusing.
• Posi Drive Motor System (PDMS): This system uses a timing belt and pulleys. Starlight offers it for heavier image trains and non Feather Touch focusers. For manual mode, you loosen a thumbscrew and turn the motor housing to slacken the belt.

Installation: A 4-Step Process on the Pinion Assembly

The HSM comes with the two Allen wrenches its installation uses, 1/16 and 7/64. The motor clamps onto the silver housing of the pinion assembly after the focus knobs are removed.

The steps: remove the gold knob and then the black knob with the 1/16 wrench; start the small pin into the gold knob and slide the clamp onto the silver housing (a snug fit, so use a gentle back and forth motion); tighten the clamping screw with the 7/64 wrench; center the gold knob in the slot and tighten it with the 1/16 wrench. Then turn the black focus knob to check the gold knob does not rub on the motor housing; if it does, loosen the clamp and move the whole assembly slightly in or out.