JMI focuser now supports Pegasus FocusCube 3

JMI has expanded compatibility for its Crayford-style electronic focuser by adding direct support for the Pegasus FocusCube 3. The integration allows users to attach the FocusCube directly to the JMI focuser using the brackets, screws, and couplers included with the FocusCube 3 package. This approach eliminates the need for extra adapters and simplifies setup for astronomers looking for automated fine focusing.

The update is designed for observers and astrophotographers using Cassegrain, Ritchey-Chrétien, and Maksutov telescopes that employ SCT rear threads. Known for producing precision-machined focusers, JMI has integrated its mechanical design with Pegasus Astro’s automation system, creating a more streamlined experience for telescope users.
Above photo credit: FarpointAstro

Features of the integration

The JMI Crayford focuser built for FocusCube 3 integration weighs 1.4 pounds and supports a maximum load of 8 pounds. Its focusing travel is 0.565 inches (14.3 mm), optimized for fine adjustments. Users begin with rough focusing through the telescope’s native focuser before relying on the JMI unit for precision control.

The focuser uses a friction-drive mechanism that prevents backlash, while also eliminating image shift during operation. Each focuser is CNC-machined, assembled, and tested in the United States, maintaining the company’s long-standing emphasis on precision.

The system arrives ready to mount the FocusCube 3, relying on the motor’s included hardware. This direct fitment ensures that users can begin using the combination without additional purchases or modifications.

Control through software and interfaces

The integration extends the JMI focuser’s utility by enabling digital control through Pegasus Astro’s software and ASCOM-compliant drivers. This allows astronomers to run automated focusing routines with widely used astrophotography programs, including NINA and Sequence Generator Pro.

Automation provides significant advantages in imaging sessions that require frequent refocusing due to environmental changes. For example, small temperature shifts during the night can alter focus, as can switching filters in an imaging sequence. The ability to run autofocus routines through software minimizes downtime and maximizes efficiency.

Compatibility with telescope designs

The integrated JMI focuser is engineered for Cassegrain, Ritchey-Chrétien, and Maksutov designs that use SCT rear threads, which remain common in amateur and professional telescopes. The 8-pound load rating supports a range of setups, including cameras, filter wheels, and other accessories, provided they remain within the specified limit.

For astronomers using Newtonian reflectors or those preferring ZWO’s EAF motor system, JMI also offers alternative focuser models designed for those needs. These variations retain the same friction-drive focus technology but adapt to different telescope and motor requirements.

Photo credit: Pegasus Astro

JMI’s background in precision focusing

JMI, originally Jim’s Mobile Inc., has been a familiar name in the astronomy accessory market for decades. Its focusers have become widely used for their mechanical reliability and smooth operation. By combining that background with digital automation from Pegasus Astro, the company is continuing a pattern of adapting to evolving practices in astrophotography.

Pegasus Astro, based in Greece, develops electronic control systems, motorized focusers, and power distribution hardware. Its FocusCube 3 is the latest generation of the company’s motorized focusing units, built for compatibility with a wide variety of telescopes.

The collaboration between JMI and Pegasus illustrates an industry trend where interoperability is emphasized, enabling astronomers to build systems that combine mechanical and electronic components from different manufacturers.

Benefits for imaging applications

Accurate focusing is one of the most critical elements in astrophotography. Even small deviations from optimal focus can reduce image sharpness and detail, particularly during long exposures. The combined JMI and FocusCube 3 system provides electronic fine control, reducing the need for manual intervention during sessions.

The autofocus capability becomes especially valuable when using filter wheels. Each filter can slightly alter the focal plane, requiring readjustment. Automated routines supported by Pegasus software and ASCOM drivers allow users to correct for these differences quickly and precisely.

By reducing the time spent manually adjusting equipment, astrophotographers can devote more of their sessions to data collection and achieve more consistent results across multiple exposures.

Availability and distribution

The JMI focuser with direct FocusCube 3 support is available through established astronomy retailers, including Farpoint Astro, which distributes JMI products. Each focuser is individually assembled and tested before shipping.

Pegasus Astro continues to market the FocusCube 3 as a universal product. Owners of the motorized focuser can use it with the new JMI units without needing additional adapters, lowering the barrier to adoption. This compatibility approach also makes the system attractive to existing Pegasus users who may want to expand their telescope equipment.

JMI focuser supports Pegasus FocusCube 3 right out of the box

The direct compatibility between JMI’s Crayford focuser and Pegasus Astro’s FocusCube 3 provides astronomers with a system that blends mechanical precision and digital control. By simplifying installation and enabling automated focusing through widely used software, the integration meets the growing demand for reliable and accessible focusing solutions. This collaboration reflects a broader movement in the astronomy community toward combining proven mechanical hardware with flexible digital automation