ZWO Mount Control

A Rust library for controlling ZWO AM5/AM3 telescope mounts via serial communication, with built-in support for satellite tracking using the keplemon crate for TLE/SGP4 propagation.

Features

• GoTo/Slewing: Command the mount to slew to any celestial coordinates
• Manual Motion: Control axis motion at various speeds (guide to max slew)
• Tracking: Enable/disable tracking with sidereal, lunar, solar, or custom rates
• Alt-Az & Equatorial Modes: Switch between altitude-azimuth and equatorial tracking
• Autoguiding: Send guide pulses for autoguiding applications
• Satellite Tracking: Track satellites using TLE data and SGP4 propagation
• Mock Mount: Test your application without physical hardware

Installation

Add to your Cargo.toml:

[dependencies]
zwo_mount_control = { git = "https://github.com/jmcguigs/zwo_mount_control" }

Quick Start

Connect to a Real Mount

use zwo_mount_control::{SerialMount, Mount, EquatorialPosition};

// Connect via serial port (typical on Linux/Mac)
let mut mount = SerialMount::new("/dev/ttyUSB0");
mount.connect()?;

// Get current position
let pos = mount.get_position()?;
println!("RA: {}h, Dec: {}°", pos.ra, pos.dec);

// Slew to Vega
let vega = EquatorialPosition::from_hms_dms(18, 36, 56.0, 38, 47, 1.0);
mount.goto_equatorial(vega)?;

Use the Mock for Testing

use zwo_mount_control::{MockMount, Mount, HorizontalPosition};

let mut mount = MockMount::new();
mount.connect()?;
mount.unpark()?;

// Set Alt-Az mode and slew to horizontal coordinates
mount.set_altaz_mode()?;
let target = HorizontalPosition::new(180.0, 45.0);
mount.goto_altaz(target)?;

Satellite Tracking

use zwo_mount_control::{SatelliteTracker, MockMount, Mount};

// ISS TLE data
let line1 = "1 25544U 98067A   24001.50000000  .00016717  00000-0  10270-3 0  9025";
let line2 = "2 25544  51.6400 208.9163 0006703  35.6028  75.3281 15.49560066429339";

let mut tracker = SatelliteTracker::from_tle(line1, line2)?;

// Set observer location (Los Angeles)
tracker.set_observer_location(34.0522, -118.2437, 71.0);

// Find next pass
let pass = tracker.find_next_pass(chrono::Utc::now(), 24.0)?;
if let Some(p) = pass {
    println!("Next pass: {}", p);
}

Examples

Basic Control (Alt-Az Slewing)

cargo run --example basic_control

This example demonstrates:

• Connecting to a mock mount
• Setting Alt-Az mode
• Going to home position
• Slewing to Az/Alt coordinates

Satellite Tracking

cargo run --example satellite_tracking -- 25544  # ISS
cargo run --example satellite_tracking -- 20580  # Hubble Space Telescope

Note: The satellite tracking example requires an SGP4 license file from Space-Track.org:

1. Create an account at https://www.space-track.org
2. Download SGP4_Open_License.txt from the site
3. Place it in the current working directory

Module Overview

Coordinate Systems

Equatorial Coordinates (RA/Dec)

Used when mount is in equatorial mode (on wedge, polar aligned):

• Right Ascension (RA): Decimal hours (0-24)
• Declination (Dec): Decimal degrees (-90 to +90)

Horizontal Coordinates (Az/Alt)

Used when mount is in Alt-Az mode (on tripod, no wedge):

• Azimuth (Az): Degrees from North (0-360°, clockwise)
• Altitude (Alt): Degrees above horizon (0-90°)

Hardware Requirements

• ZWO AM5 or AM3 mount (or compatible)
• USB-serial connection to the mount
• Serial port permissions (on Linux, add user to dialout group)

# Linux: Add user to dialout group for serial access
sudo usermod -a -G dialout $USER
# Log out and back in for changes to take effect

Dependencies

• keplemon - Satellite propagation (SGP4/TLE)
• serialport - Serial communication
• chrono - Date/time handling
• thiserror - Error types

License

MIT

Contributing

Contributions are welcome! Please feel free to submit issues and pull requests.