Sky-Watcher EQ-AL55i Pro Mount

The EQ-AL55i Pro Mount at a Glance

The payload is 10 kg (22 lb) and the head weighs 3.7 kg (8.2 lb). Two counterweights, 1.8 kg and 3.5 kg, are included.

Control is centered around modern interfaces, with built-in Wi-Fi for wireless operation via the SynScan Pro app on a smart device or computer. For wired setups, it includes a USB Type-C port for direct PC connection and an ST-4 port for standard autoguiding. The SynScan hand controller is optional.

Drive System: 73 mm Worm Wheel and 11 mm Copper Worm

The right ascension axis employs a 73 mm diameter aluminum alloy worm wheel paired with an 11 mm diameter copper worm. This gearset is driven by miniature DC servo motors.

Payload and Balance: 10 kg Capacity with Two Counterweights

The mount supports a total instrument payload of 10 kg (22 lb). To handle a range of telescope weights, it includes two counterweights: one 1.8 kg (3.9 lb) and one 3.5 kg (7.7 lb).

To balance, put the counterweight at its lowest point and check the Dec axis by loosening the Dec clutch while holding the telescope, moving the telescope in its Vixen-style saddle as needed. Then set the counterweight bar horizontal and slide the counterweight until the R.A. axis balances.

Polar Alignment: Built-in Scope with an 8.5° Field of View

The illuminated polar scope has about an 8.5° field of view. To use it, you determine the correct position for Polaris (in the Northern Hemisphere) or the Octans stars (in the Southern Hemisphere) using the SynScan Pro app's polar scope utility. You then adjust the mount's altitude and azimuth knobs to place the alignment stars in the corresponding position on the polar scope's reticle.

This gives moderate accuracy; for the best polar alignment use the drift method or camera-aided software such as PHD2 or SharpCap. The mount also features two mounting positions for the counterweight bar, the classic one for higher latitudes and a second for lower latitudes.

GoTo Control: SynScan Pro via Wi-Fi, USB, or Handset

The EQ-AL55i Pro offers three primary methods for GoTo control. The main interface is the SynScan Pro app, available for smart devices (iOS/Android) and computers (Windows), which connects to the mount's built-in Wi-Fi network.

Alternatively, you can connect a computer directly to the mount's USB Type-C port for a wired connection (USB cable sold separately). The mount also supports the optional SynScan hand controller, which connects to the dedicated RJ-45 port.

App & PC Control: Built-in Wi-Fi, USB-C, and ASCOM

To operate the mount wirelessly, you connect your device to the Wi-Fi network broadcast by the mount, which will appear as "SynScan_xxxx". Once connected, the SynScan Pro app can connect to the mount. If your device uses Wi-Fi for its internet connection, it will lose that connection while joined to the mount.

For PC control, the manual has you install the latest ASCOM platform, Sky-Watcher's ASCOM driver and the SynScan Pro app for Windows, connect the mount by USB, and connect SynScan Pro over the serial (COM) port. Your guiding software then connects to the mount following its own instructions.

Imaging Integration: ST-4 Guiding and 2.5 mm SNAP Port

An autoguide port (ST-4, RJ-12) allows you to connect a guide camera for sending tracking corrections. The ST-4 guide cable is sold separately.

The mount also includes a 2.5 mm SNAP port for camera shutter control. By connecting a compatible shutter release cable (sold separately) from this port to your camera, you can trigger exposures automatically through the SynScan Pro app.

Tripod and Saddle

The mount head attaches to the included adjustable-height tripod, which features a bubble level to ensure the base is horizontal. An accessory tray fits between the tripod legs. The mount head includes a standard Vixen-style (V) dovetail saddle.

Power System: 9V to 12.6V DC Input Requirements

The EQ-AL55i Pro requires a DC power source between 9 V and 12.6 V, capable of supplying at least 1.5 A of current. The input is a center-positive barrel plug with a 2.0 mm internal diameter and 5.5 mm outer diameter. A DC power cable is included, but the power supply itself is not.

Do not use an unregulated AC-to-DC adapter; use a switching power supply with 12 V output and at least 1.5 A. Voltage outside the range can cause permanent damage. If the voltage is too high, the motor controller stops the motors.

First Night Setup: Assembly, Balancing, and Alignment

Setting up the EQ-AL55i Pro for the first time goes like this. First, expand the tripod legs on level ground and adjust their height, using the bubble level to make the tripod top horizontal. Next, seat the mount head onto the tripod, ensuring the tripod's alignment pin is between the two azimuth adjustment knobs, and turn the screw bar to attach it.

Attach the accessory tray to brace the tripod legs. Set the latitude scale on the mount to match your observing location. Install the counterweight bar, slide on the necessary counterweights, and attach your telescope to the Vixen-style saddle. Perform the two-axis balancing procedure, and you are ready to power on the mount and begin polar alignment using the built-in polar scope.

Weights

The mount head weighs 3.7 kg (8.2 lb). The entire package, including the tripod, counterweights, and accessories, has a shipping weight of 14.8 kg (32.6 lb).