Skip to content
Price match 30-day returns* Talk to an astronomer before you buy
RB Focus Merlin HD 3.0 Heavy Duty Electronic Focuser
RB Focus Merlin HD 3.0 Heavy Duty Electronic Focuser
RB Focus Merlin HD 3.0 Heavy Duty Electronic Focuser
RB Focus Merlin HD 3.0 Heavy Duty Electronic Focuser
RB Focus Merlin HD 3.0 Heavy Duty Electronic Focuser
RB Focus Merlin HD 3.0 Heavy Duty Electronic Focuser
RB Focus Merlin HD 3.0 Heavy Duty Electronic Focuser
RB Focus Merlin HD 3.0 Heavy Duty Electronic Focuser

RB Focus Merlin HD 3.0 Heavy Duty Electronic Focuser

by RB Focus
SKU RB-MERLINHD3-MAK127
CA$462.00 - CA$520.00
CA$495.00
CA$462.00 - CA$520.00
CA$495.00
Price Match Policy!
  • Heavy Duty version of the Merlin 3.0, NEMA 17 motor
  • 0.7 micron precision
  • 16,000 steps per revolution for extremely fine adjustments
  • USB 2.0 and Bluetooth connectivity for wired or wireless control
  • ASCOM and INDI compatible
  • Temperature sensor included
Backordered
Request Stock Alert
Availability Info
Qualifies for FREE Shipping in Canada on orders over $500.
Focus Step Calculator

Set the right autofocus step

Get the autofocus step size for the RB Focus Merlin HD 3.0 Heavy Duty Electronic Focuser with your telescope and camera, in each capture program.

Calculate step size
  • Description
  • FAQ
  • Specifications
  • In the Box
  • Warranty

  • RB Focus Merlin HD 3.0 Heavy Duty Electronic Focuser

    The RB Focus Merlin HD 3.0 is the Heavy Duty version of RB Focus's Merlin 3.0 focus motor. It automates your telescope's existing focuser with a NEMA 17 motor, 16,000 steps per revolution (0.7 microns), USB 2.0 and Bluetooth, and runs on 12V DC. RB Focus makes it in Spain, CNC-machined from aluminum, and says it works with any camera from DSLRs to mono cameras.

    0.7 Micron Precision from 16,000 Steps Per Revolution

    The Merlin HD 3.0 moves your focuser with a resolution of 16,000 steps per revolution, or a precision of 0.7 microns. RB Focus says autofocus with it reaches focus more precisely than a Bahtinov mask, without slewing the telescope to a bright star.

    Its DirectDrive (direct transmission) avoids the mechanical play common in other products, and RB Focus notes it even lets you focus manually when you have no computer at hand. The InteligentSilentDrive system actively adjusts the motor's force for completely silent operation.

    Sensorless AutoHoming and Magnetic Tension Sensing

    Sensorless AutoHoming automatically calibrates the focuser in several directions. If the tube is moved by accident, or you rack the focuser in by hand at the end of the session, it returns the focuser to the last focus point applied by your capture program, so position is not lost.

    A magnetic-field sensing system ensures the correct tension on the focuser mechanism, avoiding unwanted slippage.

    Dual-Core Processing and Auto-Off IPS Display

    A Dual Core processor runs autofocus without interruption while it refreshes the display and handles its other functions.

    The full-color IPS LCD screen, with automatic on/off, lets you check that the focuser is working correctly, review saved settings and follow its movements in real time without looking at your computer.

    USB 2.0, Bluetooth, and Mobile App Control

    The Merlin HD 3.0 connects to your computer by USB 2.0, and its Bluetooth antennas reduce cables and weight on your setup.

    When you're observing visually or doing planetary imaging, you can bypass a laptop entirely. The RB Focus mobile app connects to the Merlin HD 3.0 via Bluetooth, giving you an intuitive interface for making manual focus adjustments directly from your smartphone.

    Native ASCOM and INDI Compatibility

    Through the ASCOM and INDI standards, the Merlin HD 3.0 works with the capture programs RB Focus names: APT, SGP, N.I.N.A., Voyager, KStars and Ekos.

    Brackets and Adapters for SCT, Crayford, and Takahashi Focusers

    The Merlin HD 3.0 is designed to motorize your telescope's existing focuser. The kit includes a versatile self-aligning shaft coupler and adapters for common shaft diameters of 2.5mm, 4mm, and a 3.5mm adapter specifically for Takahashi focusers. An adapter for dual-speed Crayford focusers with a 27mm reducer is also included.

    Choose the bracket format for your focuser: Standard format (Sky-Watcher models with dual-speed focuser, TS, GSO, William Optics and similar), Large format (Feather Touch and similar), Mak 127 base, SCT base (Mak 150 and larger), or the Takahashi adapter (27 mm with 3.5 mm shaft).

  • Will the RB Focus Merlin HD 3.0 fit my Celestron 8" SCT?

    Choose the SCT base version. RB Focus lists Celestron and Meade SCTs and Sky-Watcher Maksutovs for its SCT format and asks you to confirm the size, so ask us before ordering.

    What makes the Merlin HD 3.0 "Heavy Duty"?

    RB Focus presents it as the Heavy Duty version of the Merlin 3.0 but does not detail what differs from the standard model. Ask us if you need to compare them.

    Do I need to buy a separate power adapter for the Merlin HD 3.0?

    Yes. No power adapter is included (RB Focus sells one separately). It runs on 12V DC through a 2.1 x 5.5 mm DC jack.

    How does the included temperature sensor work with the Merlin HD 3.0?

    The sensor reports temperature to your capture software, so software that supports it can refocus as the temperature changes during the night.

    Can I still focus my telescope manually with the Merlin HD 3.0 installed?

    RB Focus says the DirectDrive transmission lets you focus manually even when you have no computer at hand, and the mobile app allows manual electronic focusing over Bluetooth. RB Focus does not say whether the focuser knob can be turned by hand with the motor fitted.

    What is Sensorless AutoHoming on the Merlin HD 3.0?

    RB Focus's Sensorless AutoHoming automatically calibrates the focuser in several directions. If the tube is moved by accident or racked in by hand, it returns the focuser to the last focus point applied by your capture program.

    Is the Merlin HD 3.0 effective for focusing a DSLR on an f/4 Newtonian?

    Yes. RB Focus says the Merlin works equally well with color cameras and DSLRs as with mono cameras, on reflectors and refractors.

    What software do I need to use the RB Focus Merlin HD 3.0?

    The Merlin HD 3.0 requires imaging software that supports ASCOM (on Windows) or INDI (on Linux/macOS) focusers. Popular compatible programs include N.I.N.A., Sequence Generator Pro (SGP), APT, Voyager, and KStars/Ekos. You will need to install the appropriate ASCOM or INDI driver for the Merlin HD 3.0.

    How do I control the Merlin HD 3.0 with Bluetooth?

    Use the RB Focus mobile app on your phone for manual focusing over Bluetooth.

    What is the advantage of the 16,000 steps per revolution on the Merlin HD 3.0?

    A high step count of 16,000 steps per revolution allows the motor to make extremely small, precise rotational movements. This fine control is what enables the focuser to achieve its high precision of 0.7 microns per step, ensuring it can hit the exact point of critical focus identified by your software.

  • Motor NEMA 17
    Precision 0.7 microns
    Step resolution 16,000 steps per revolution
    Display Full-color IPS LCD with automatic on/off
    Data interface USB 2.0
    Wireless Bluetooth
    Compatibility ASCOM and INDI software
    Power 12V DC
    Power connector 2.1 x 5.5 mm DC jack
    Temperature sensor Included

    • RB Focus electronic focus motor

      × 1

    • Temperature sensor

      × 1

    • USB Type-A to USB Type-C cable

      × 1

    • Self-aligning shaft coupler

      × 1

    • Shaft adapters 4 mm, 2.5 mm and 3.5 mm (Takahashi)

      × 1 set

    • Adapter for dual-speed Crayford focusers with 27 mm reducer

      × 1

  • RB Focus 2-Year Warranty