OnStepX SWS Control

Alessandro Cimarelli

About this app

OnStepX SWS Control is an independent Android client for telescope mounts running OnStepX firmware, over WiFi (TCP) or Bluetooth Classic (SPP). It uses only the local network or Bluetooth, so it works in the field with no Internet.

NOT OFFICIAL
An independent app, not affiliated with the OnStep project or its authors. It needs a mount with OnStepX firmware already installed and working: the app does not install or update firmware.

CONNECTION
• WiFi profiles with host or IP and port; Bluetooth profiles from devices already paired
• Search for OnStep mounts on the local network
• Optional auto reconnection and checksums for noisy links
• Keeps the session alive with the screen off, if enabled

POINTING
• Directional pad at 1x, 8x, 20x, 48x and maximum rate
• STOP always available while the mount moves, plus an automatic halt if the button release is lost
• GoTo and sync on objects or on typed RA/Dec coordinates
• Warning before a GoTo when the object will pass the overhead limit while tracking
• Park, unpark, go home, spiral search
• Multi-star alignment with suggested stars; polar alignment refinement on equatorial mounts

CATALOGS AND MAP, OFFLINE
• About 16,000 deep-sky objects: Messier, NGC/IC (OpenNGC), Caldwell, Sharpless, van den Bergh, Barnard, LDN, Abell planetary nebulae, Arp galaxies
• 15,554 stars to magnitude 7, search by name, designation or full Bayer name (e.g. Epsilon Draconis)
• Sun, Moon and planets computed on the phone, with altitude and azimuth
• Interactive sky map: constellation lines and names, star colors, Alt/Az grid (RA/Dec on equatorial mounts) with adjustable brightness, field of view (FOV) frame for camera or eyepiece, zoom, filters by object type, scope following, tap to GoTo

MOUNT
• Tracking: sidereal, lunar, solar and King; automatic tracking rate for the Sun and Moon after a GoTo; refraction or full compensation on one or both axes; slew speed; buzzer
• Horizon, overhead and meridian limits, automatic meridian flip, home and park, backlash
• Per-axis motors and drivers: status, steps per degree, microsteps, currents, acceleration and more

PERIODIC ERROR CORRECTION (PEC)
• Recording and playback with a progress bar over the period
• Chart of the recorded curve, write to EEPROM, steps per period

FOCUSER, ROTATOR, AUXILIARY
• Focusers: position in steps or microns, manual and absolute moves, backlash, temperature compensation
• Rotator: angle, moves, parallactic angle, derotator
• Switches and outputs, dew heater driven by the dew point, intervalometer

WEATHER
• Temperature, humidity, pressure and dew point from the mount sensor, 72-hour history on the phone with charts

DATE, TIME AND SITE
• Date, time and site sent from the phone; the location comes from GPS or, without it, from the network

SAFETY AND COMFORT
• Changes to the firmware configuration can be protected by the phone unlock or an app PIN
• Light, Dark and Night (red) themes with adjustable brightness
• Six languages: English, Italian, German, French, Spanish and Portuguese
• Pages stay readable at every text size set on the phone
• Demo mode with a simulated mount, to try the app without hardware

PRO FEATURES
All the features for operating the mount stay free. From 1 March 2027 some advanced features (sky map, catalog GoTo, guided alignment, PEC, weather history, advanced axis settings, rotator, focuser temperature compensation) will need a Pro unlock, a one-time in-app purchase with no subscription.

PRIVACY
No account, no advertising, no analytics, no data collection, nothing sent to any server. Profiles, settings and the weather history stay on the phone. Location is used only to set the observing site and goes to the mount alone.

What’s new

Control page: if a confirmation dialog appears while holding a slew button, the mount stops immediately.