EQ Focuser

EQFocuser is a custom-built, ASCOM-compatible motorized focuser designed to provide precise, temperature-compensated, automated focusing for astrophotography rigs. Created for hobbyists and enthusiasts who demand accuracy and automation from their imaging sessions, EQFocuser offers a reliable, customizable solution for achieving critical focus—especially for deep-sky and narrowband imaging.

Built with Arduino hardware and a C# ASCOM driver, EQFocuser integrates directly into astrophotography workflows using tools like NINA, Sequence Generator Pro (SGP), and other ASCOM-aware applications.

Manual focusing during astrophotography, especially in varying nighttime temperatures, introduces inconsistencies that can ruin an imaging session. Commercial electronic focusers are often expensive or limited in compatibility. I designed EQFocuser as an open-source, budget-friendly, and adaptable alternative with full ASCOM support.

• ASCOM Focuser Compatibility
  Seamlessly integrates with Windows-based astrophotography software like NINA, SGP, and SharpCap using the ASCOM platform.

• Microstepping Precision via Stepper Motor
  Uses A4988 or DRV8825 stepper drivers to achieve microstepping focus control for sub-millimeter accuracy.

• Customizable Focus Travel and Limits
  Allows users to define min/max travel limits and microsteps per millimeter for compatibility with various focusers (Crayford, Rack & Pinion, etc.).

• Temperature Compensation (Optional)
  Supports a temperature sensor (e.g., Dallas DS18B20) to track temperature changes and adjust focus accordingly over long sessions.

• Backlash Compensation
  Software-enabled backlash handling ensures accurate bidirectional focusing—a crucial feature when changing directions during autofocusing.

• USB Connectivity via Arduino Nano
  Connects over USB to your PC, where the ASCOM driver interfaces with your control software.

• DIY-Friendly and Affordable
  Uses off-the-shelf components and is easy to build for under $40 USD.

• ✅ Arduino firmware for USB communication and stepper control
• ✅ Custom ASCOM driver built in C#
• ✅ Wiring diagrams and component list
• ✅ ASCOM driver installer and source code
• ✅ Basic instructions for NINA and SGP integration
• ✅ STL mount files (optional: upload to GitHub)

• Arduino Nano (ATmega328P-based)
• Stepper motor (e.g., NEMA 17)
• Stepper driver (A4988 or DRV8825)
• Temperature sensor (DS18B20, optional)
• External 12V power supply
• Pulley or flexible shaft coupler (based on focuser type)
• USB cable for Arduino
• Mount/bracket for stepper motor (3D printed or machined)

1. Flash the Arduino Nano
   Upload the firmware from the firmware folder using Arduino IDE.

2. Install the ASCOM Platform
   Download and install ASCOM Platform.

3. Install EQFocuser Driver
   Run the .exe installer from the driver folder to register the focuser.

4. Connect to Imaging Software
   Open NINA or SGP, go to the focuser settings, and choose "EQFocuser" as the device.

5. Configure Steps per mm
   Use your software's settings to tune the steps per revolution, backlash, and temperature compensation.

I’ve used EQFocuser in live astrophotography sessions under various conditions with my Explore Scientific ED127mm triplet APO and ZWO ASI1600MM Pro camera. Focus precision was maintained throughout long exposures and filter changes, especially when using narrowband filters where focus shifts are significant. Autofocus routines performed via NINA showed repeatable, stable V-curves even over several hours.

EQFocuser is entirely open-source. Whether you're a maker, an astrophotographer, or just curious, feel free to fork, contribute, or adapt the project to your own telescope. I welcome community improvements and would love to see this adapted to more platforms—such as INDI for Linux users.

🔗 GitHub Repo: github.com/EverettQuebral/EQFocuser

• Support for INDI and Linux integration
• OLED display showing position and temperature
• WiFi/ESP32 version for cable-free setups
• Support for absolute position encoding
• 3D printable enclosure and geared mount for Crayford focusers