PrimaLuceLab ESATTO 3" Robotic microFocuser

A Crayford System Built for an 8 kg Payload

The ESATTO 3" uses a modified Crayford-style design that runs on steel ball bearings (steel rather than stainless, for the load capacity; the manual notes they can show oxidation in high humidity and can be cleaned with a product like WD40). It carries up to 8 kg. The manual explains that a focuser without enough load capacity lets heavy imaging trains slip out of focus, especially near the zenith.

With the optional telescope adapters, the ESATTO 3" can replace the standard focuser of many telescopes. The manual notes that a very small image shift during movement is normal with the modified Crayford design.

25mm of Travel at 0.04 Micron Resolution

The ESATTO 3" has a resolution of 0.04 microns per step and 25mm of draw tube travel. With telescopes whose original focuser has longer travel, the manual says you may need one or more extension tubes to reach focus.

While the Crayford design offers exceptional smoothness, it's important to note that minor variations in step position can occur over many repeated autofocus runs, especially with very fast optics. This is normal behavior for this mechanical design and is distinct from backlash. If you notice a gradual drift, run a new automatic calibration in PLAY, especially when the change exceeds half of the draw tube travel; it resets the internal reference.

76.3mm Aperture in a 77mm Body

The ESATTO 3" has a 76.3mm free aperture.

All of this is contained within a housing that has a body thickness of 77mm, including its mounting flange. The manual shows it on GSO Ritchey-Chretien 10" to 16" telescopes (also truss) with the PL3600236 adapter, and PrimaLuceLab makes ESATTO 3" adapters for refractors such as Takahashi, Sky-Watcher Esprit and Borg models.

M81x1 Threads and Telescope Adapters

The ESATTO 3" draw tube ends in an M81x1 male thread. PrimaLuceLab's optional camera adapters go from M81 with stop ring to T2, M48, M54, M57, M68 or M72, and there are M81 extension tubes (25mm, 40mm and 65mm) and 2" and 3" visual backs.

Optional telescope-side adapters include:

• GSO/Orion/TPO Ritchey-Chrétiens: PL3600236 for the 10", 12", 14" and 16" models (also truss).
• Refractors: adapters for Takahashi FSQ85, TSA 120 and telescopes with M72 thread, Sky-Watcher Esprit 80, 100 and 120/150 ED, and Borg 90FL and 107FL, among others.

USB-C, WiFi, and ASCOM for Full Remote Operation

The control electronics are built into the focuser, so no external controller is needed. Ways to control it:

• USB-C Connection: Connect the ESATTO directly to a PrimaLuceLab EAGLE or any Windows 10/11 computer using the included USB-C to USB cable.
• WiFi Virtual HandPad: For visual use or setup without a computer, you can connect to the ESATTO's built-in WiFi network from any smartphone or tablet. The included Virtual HandPad moves the focuser and saves up to 9 named focus positions.
• PLAY Software: PrimaLuceLab's own PLAY software provides a unified interface for controlling the ESATTO and other compatible devices.
• ASCOM Driver: An ASCOM driver (tested with ASCOM platform 7) is provided for control from third-party software.

Internal Sensor and External Probe Port for Temperature Compensation

Focus can shift as temperature changes. The ESATTO 3" has an internal sensor that reads the motor temperature. For more precise temperature compensation, an optional external temperature probe can be connected to a dedicated port.

With the probe connected, the ESATTO reports temperature with its position, and autofocus can be set to run after a temperature change.

Internal Sensors for Automatic Travel Limit Calibration

Thanks to its calibration sensor, the ESATTO 3" detects its max in and max out positions, and every unit is already calibrated in PrimaLuceLab's factory.

This calibration data is stored directly in the focuser's memory, so you don't need to calibrate when switching computers. If needed, a new calibration runs from PLAY (usually 2 to 3 minutes) or the Virtual HandPad.

The Dedicated ARCO Port for Robotic Rotation

The ESATTO 3" has a port for the optional ARCO rotator, which is powered and controlled through it with the ARCO cable, so no separate 12V or USB cable goes to the rotator. The Adapter ESATTO 3" for ARCO 3" joins the two.

With ARCO you can remotely set the camera rotation angle for framing. For users with alt-azimuth mounts, the ARCO can also function as a field de-rotator, enabling long-exposure astrophotography without an equatorial wedge.

12V and USB-C Power Options

The ESATTO 3" offers flexibility in how it is powered. It can be powered through the USB connection from an EAGLE or computer. If a computer's USB ports deliver less than 0.5A, the focuser may stop abruptly, and you must also connect 12V.

The 12V port (5.5/2.5 connector, positive tip; maximum 350mA at 12V) takes the included cigarette plug cable. For WiFi control from a 12V supply, use at least 1A.

ESATTO 3" vs. ESATTO 2": Aperture and Payload

Both have the same resolution (0.04 microns per step) and the same control options.

The ESATTO 3" has a 76.3mm free aperture (51mm on the 2"), 8 kg payload (5 kg), 25mm travel (15mm), a 77mm body including flange (67mm) and weighs 1345 g (835 g). For SCT and EdgeHD telescopes the 2" is the recommended model.