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IMPORTANT: Our store is located in Canada. All orders that include products manufactured outside of Canada or USA will be subject to tariffs and duties, regardless of the order value. US customers are responsible for all applicable duties and tariffs, and those will be billed by the carrier, except for the Lacerta upgrade kit, for which we collect them at checkout.
IMPORTANT: Our store is located in Canada. All orders that include products manufactured outside of Canada or USA will be subject to tariffs and duties, regardless of the order value. US customers are responsible for all applicable duties and tariffs, and those will be billed by the carrier, except for the Lacerta upgrade kit, for which we collect them at checkout.
iOptron iAFS3 - 3-inch Inline Automatic Focuser

iOptron iAFS3 - 3-inch Inline Automatic Focuser

by iOptron
SKU IOP-FA30
$539.00 - $539.00
$539.00
$539.00 - $539.00
$539.00
Price Match Policy!
  • 3-inch inline auto focuser with iLock™ technology
  • Supports heavy imaging payloads up to 6kg
  • 68mm clear aperture minimizes vignetting
  • Precise 0.4um focusing resolution
  • 30mm of drawtube travel distance
  • ASCOM and INDI compliant for computer control
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  • Description
  • FAQ
  • Specifications
  • In the Box
  • Warranty

  • iOptron iAFS3 - 3-inch Inline Automatic Focuser

    The iOptron iAFS3 is a 3-inch inline automatic focuser engineered to eliminate mechanical shift, supporting imaging payloads up to 6kg with its patented iLock™ technology. A generous 68mm clear aperture provides unvignetted fields for large sensors, while the stepper motor achieves a focusing resolution of 0.4um over 30mm of travel. Weighing 1062g and featuring dual USB-C ports, the iAFS3 integrates seamlessly into advanced imaging setups requiring absolute focus stability.

    iLock™ Technology: Zero-Shift Focusing for 6kg Payloads

    At the core of the iAFS3 is iOptron's iLock™ system, which uses a lead worm movement to passively lock the drawtube's position the instant the motor stops. This design prevents any focus drift or slippage, even when a heavy 6kg payload of a camera, filter wheel, and off-axis guider is pointed near the zenith. This mechanical certainty ensures that the focuser's precise 0.4um step size translates directly to sharp stars, without any backlash or flexure compromising your data.

    Triple Control System: ASCOM, Onboard Buttons, and Manual Override

    The iAFS3 offers three distinct methods of control for complete flexibility in the field. For fully automated sessions, it connects to your PC via one of two USB-C ports and is controlled through ASCOM or INDI drivers in software like NINA or SGP, using data from the built-in temperature sensor to maintain focus all night. For quick adjustments at the telescope, integrated motorized buttons allow for powered focusing without a computer, while a manual override wheel gives you tactile control for initial setup or situations where power is unavailable.

    Engineered for Large Imaging Trains: 68mm Aperture and 30mm of Travel

    Designed specifically for serious astrophotography, the iAFS3 features a large 68mm clear aperture to illuminate full-frame and larger sensors without vignetting. Its 30mm of drawtube travel provides sufficient range to achieve focus with various accessories and optical configurations. The focuser also includes a camera angle adjustment mechanism, allowing you to perfectly frame your target without disturbing the optical train. While a 2" visual back is included, you will need to acquire the appropriate telescope-side adapter to match your specific instrument.

    iOptron iAFS3 vs. iAFS2: Choosing the Right Focuser Size

    The primary difference between the iAFS3 and its 2-inch sibling, the iAFS2, is the clear aperture and intended application. The iAFS2 is a more compact and lighter option, ideal for smaller refractors and systems using APS-C or smaller sensors where the larger barrel of the iAFS3 is unnecessary.

    You should choose the 3-inch iAFS3 when your imaging train involves a full-frame or larger format sensor, or when you are using a large aperture telescope where a 2-inch focuser would become a bottleneck in the light path. The iAFS3's 68mm clear aperture is essential for preventing vignetting and ensuring even illumination across these larger fields of view.

  • What is the main benefit of the iOptron iAFS3's iLock™ technology?

    The iLock™ technology uses a lead worm drive that passively locks the focuser's position when the motor is not moving. This completely prevents the drawtube from slipping or shifting under the weight of a heavy camera, ensuring your focus remains perfect regardless of the telescope's orientation. It's critical for maintaining sharpness during long exposures or automated imaging runs.

    How does the iOptron iAFS3 handle a heavy payload on a large SCT?

    The iAFS3 is rated for a maximum payload of 6kg (13.2 lbs), making it more than capable of handling a typical imaging train with a cooled camera, large filter wheel, and off-axis guider. The rigid, all-metal body and iLock mechanism ensure there is no flexure or drift, even on a system with a moving primary mirror like a Schmidt-Cassegrain Telescope.

    Can I control the iOptron iAFS3 without a computer?

    Yes. The iAFS3 has two non-computer control methods. It features onboard motorized focusing buttons for powered, push-button adjustments at the telescope. It also includes a manual focusing wheel that overrides the motor, allowing for fine, tactile control without any power required.

    What adapters do I need to connect the iOptron iAFS3 to my telescope?

    The iOptron iAFS3 does not include a telescope-side adapter. You must purchase an adapter specifically designed to connect the iAFS3 to your telescope's particular rear thread or visual back type (e.g., M68, SCT 3.25", etc.). iOptron offers a range of optional adapters to fit various OTAs.

    What is the purpose of the built-in temperature sensor on the iAFS3?

    The built-in temperature sensor allows automatic focusing software (via ASCOM/INDI) to monitor ambient temperature changes throughout the night. As the temperature drops, the optical tube can contract, causing the focal point to shift. The software uses the sensor's data to trigger periodic refocusing routines, ensuring your images remain critically sharp from dusk till dawn.

    Will the iOptron iAFS3 cause vignetting with my full-frame camera on a fast refractor?

    The iAFS3 is specifically designed to prevent vignetting in such scenarios. Its large 68mm clear aperture provides a wide, unobstructed light path that can fully illuminate sensors up to and beyond the standard 35mm full-frame format, even when used with fast optical systems.

  • Focuser Size 3"
    Focuser Type Inline Auto Focuser with iLock™
    Maximum Payload 6kg
    Clear Aperture 68mm
    Drawtube Travel 30mm
    Focusing Resolution 0.4um
    Drive System Stepper motor
    Computer Control Yes (ASCOM and INDI)
    Automatic Focusing Yes
    Manual Control Motorized Buttons & Manual Override Wheel
    Ports 2x Type-C USB2.0
    Temperature Sensor Yes (Built-in)
    Camera Angle Adjustment Yes
    Dimensions 94 x 133 x 108mm
    Weight 1062g
    Shipping Weight & Dimensions 4 lbs, 11 x 8 x 7 in

    • iAFS3 Focuser Body

      × 1

    • 2" Visual Back

      × 1

  • iOptron 2-Year Limited Warranty