User Guide
Complete Feature Reference
Every panel, control, and workflow in OpenSkyLab explained. All features described here are included in the free, open-source core unless marked with a PRO badge.
Interactive Sky Map
The sky map is a WebGL-rendered 3D sky view powered by Three.js. It displays over 100 million stars, 530+ deep-sky objects, 35 constellations, planets, and the Milky Way — all rendered in real-time.
Embedded Catalogs (Offline)
| Catalog | Objects | Details |
|---|
| Messier | 110 | All objects with popular names |
| Caldwell | 109 | Complete Caldwell catalog |
| NGC | 210+ | Notable NGC, mag 11.5 and brighter |
| IC | ~100 | Notable IC objects |
| Named Stars | ~240 | Hipparcos J2000 coordinates |
| Constellations | 35 | IAU stick-figure lines |
Unified Search
Search by catalog number (M42, NGC 2903), popular name (Orion Nebula), or star name (Sirius, Vega). Supports multi-language aliases for solar system objects (Sol, Lua, Marte in Portuguese).
Time Travel
Scrub through time with date picker, hour slider (1-minute steps), and step buttons (+-1h, +-1d, +-1y). See where objects will be at any point in the future or past. Reset to current time with one click.
HiPS Background
Download sky survey tiles (HiPS) for background imagery. 5 detail levels cached locally for offline use. Pre-download regions centered on your targets.
Camera Control
Full camera control with exposure, gain, offset, binning, ROI, and cooler management. Supports INDI, ASCOM Alpaca, and DSLR/Mirrorless cameras (CR2, CR3, ARW via libraw).
Exposure Controls
Set duration (0.001s to 3600s), gain, offset, binning (1x1 to 4x4), and frame type (Light, Dark, Flat, Bias). ROI support for faster readout on high-resolution sensors.
Cooler Management
Set target temperature, monitor current temperature, and power percentage. Visual indicator shows cooling progress and stability.
Frame Browser
Table view of all captured frames with HFR, FWHM, star count, and file path. Click any frame to open it in the FITS Viewer.
Flat Wizard
Automatically finds the optimal exposure time for flat frames by targeting a specific ADU value. Iterative algorithm converges in 3-5 iterations.
Frame Analysis
Every captured frame is automatically analyzed for focus and optical quality — no separate tool required. Results appear in the Frame Browser and the live exposure graph as frames come in.
HFR & FWHM
Half-Flux Radius and Full Width at Half Maximum are computed per frame from detected stars, giving you an immediate read on focus sharpness across the session.
Star Count
Total detected stars per frame. A sudden drop signals passing clouds, dew on the optics, or a focus/tracking problem worth investigating.
Distortion Analysis
Analyzes plate-solved frames for optical distortion (coma, field tilt) across the field of view, helping diagnose collimation or spacing issues before you shoot hundreds of subs.
Blink Comparator
Compare captured frames side by side to catch problems that a single frame won't reveal — tracking drift, focus shift between filters, or an intruding satellite or plane.
Frame Comparison
Select two or more frames from the Frame Browser to create a blink session, then flip between them to spot differences frame-to-frame.
Synchronized Pan/Zoom
Pan and zoom stay locked across all frames in the session, so you're always comparing the exact same region of sky while blinking.
Sub-Exposure Time Calculator
Calculates the optimal single-sub exposure time from your camera's read noise, the sky background flux at your location, and a desired swamp ratio — so you don't waste imaging time on subs longer than necessary just to swamp read noise.
Inputs & Result
Enter read noise (e-) and sky flux (e-/s), pick a target swamp ratio (typically 3-10x read noise), and the calculator returns the recommended exposure time for that filter and sky brightness.
Flat Panel & Sky Flats
Control a motorized flat panel or flat cover directly from OpenSkyLab, and capture calibration flats without leaving the app.
Flat Panel Control
Set panel brightness percentage, power the panel on/off, and open/close a motorized cover — supports INDI and ASCOM Alpaca flat panels.
Automated Sky Flats
Captures dawn or dusk sky flats automatically, tracking changing twilight brightness and adjusting exposure time each frame to keep hitting the target ADU.
Calibration Frame Library
A managed library of dark and flat calibration frames, indexed so the sequencer always applies the right calibration to the right light frame.
Library Management
Add individual calibration frames or batch-import a folder. Frames are indexed by exposure time, gain, offset, sensor temperature, and binning.
Auto-Match
When processing or reviewing a session, OpenSkyLab automatically matches the best available calibration frame to each light frame's settings.
Framing Assistant
Compose your shot before committing telescope time to it.
Field of View Overlay
Overlays your camera's field of view — computed from your equipment profile's focal length and sensor size — on the Sky Map or a plate-solved reference frame, including rotation from the current camera/rotator angle.
Composition Preview
Nudge target coordinates and rotation to fine-tune framing around a subject before starting a sequence, avoiding wasted subs on a poorly composed shot.
Mount & GoTo
Control your mount with GoTo, sync, tracking modes, park/unpark, and meridian flip management.
GoTo
Enter RA/DEC coordinates manually or click any object on the Sky Map. The mount slews to the target and tracking begins automatically.
Tracking Modes
Sidereal (stars), Lunar, Solar, or Off. Switch modes for different target types.
Meridian Flip
Configurable hour angle limit and direction. When the limit is reached during a sequence, the system automatically flips, re-solves, re-centers, and re-starts guiding.
Pointing Model
Build a multi-star alignment model. Add alignment points (solved positions vs. reported positions) to improve GoTo accuracy across the sky.
Mosaic PlanningPRO
A Pro plugin for planning and capturing multi-panel mosaics that exceed a single frame's field of view — framing large targets like the Andromeda Galaxy or the Rho Ophiuchi complex across several tiles.
Panel Grid
Specify the mosaic center (RA/DEC), per-panel field of view, overlap percentage, and row/column count. OpenSkyLab computes the center coordinates for every panel automatically.
Mosaic Capture
Queues a sequence for each panel with automatic slew, plate solve, and sync between panels, so the whole mosaic runs unattended.
Sequencer
The sequencer engine automates multi-target, multi-filter imaging sessions with dithering, autofocus triggers, and checkpoint recovery.
Sequence Steps
Each step defines: filter, exposure time, gain, offset, binning, frame count, dither interval, and focus offset. Steps execute in order with automatic filter changes.
Advanced Conditions & Triggers
Define conditions for step execution (altitude limits, time windows) and triggers (autofocus every N frames, temperature drift threshold).
Checkpoint Recovery
If power is lost or the daemon crashes, the sequencer saves progress to disk. On restart, resume from the exact frame where you left off.
Templates
Save and share sequence configurations as templates. Create, edit, clone, and apply templates from the Template Browser.
Autoguiding (PHD2)
Integrated with PHD2 via JSON-RPC. Real-time RMS statistics, dither control, guide star monitoring, and calibration — all from within the OpenSkyLab UI.
Guide Graph
High-performance uPlot chart showing RA and DEC corrections in real time. RMS values displayed with color-coded quality indicators.
Dithering
Configurable dither amount (pixels) and settle time. Dithering integrates with the sequencer — dither every N frames automatically.
Autofocus (V-Curve)
Automated V-curve focusing with HFR measurement. The algorithm captures frames at different focus positions, fits a V-curve, and moves to the minimum HFR position.
Configuration
Step size, number of steps (typically 9), tolerance threshold, and backlash compensation. Per-filter focus offsets are applied automatically when the filter changes.
Temperature Compensation
Optional coefficient-based compensation that adjusts focus position based on temperature drift from the focuser's temperature sensor.
Target Scheduler
Multi-night observation planner. Define targets with constraints, and the scheduler automatically picks the best target based on altitude, moon distance, and priority.
Target Constraints
Minimum altitude, moon separation distance, time window (start/end), maximum airmass. Targets that don't meet constraints are skipped.
Automated Workflow
For each target: slew, plate solve, sync, start guiding, run sequence. On completion, move to the next best target. Auto-park when all targets are done or weather becomes unsafe.
Polar Alignment Wizard
Automated three-point polar alignment. The wizard captures and solves three frames while rotating the mount, then computes the precise altitude and azimuth error.
Workflow
Start wizard, capture first frame (auto-solve), rotate mount 90 degrees, capture second frame, rotate again, capture third frame. Error computed automatically with directional correction arrows.
Iterative Refinement
After making physical adjustments to your mount, re-measure to verify improvement. History of measurements shown for tracking progress toward perfect alignment.
Live Stacking
Real-time sub-pixel aligned stacking with sigma-clip rejection. Watch your deep-sky target emerge as frames accumulate during the imaging session.
Alignment
Sub-pixel registration using star matching. Each new frame is aligned to the reference frame before stacking.
Rejection
Sigma-clip rejection removes outliers (satellites, cosmic rays, hot pixels) for cleaner results.
FITS Viewer
Full-featured FITS viewer with zoom, pan, auto-stretch, and WCS coordinate overlay. Interactive per-channel RGB histogram with log scale and stretch presets.
Stretch Modes
Auto-stretch, linear, logarithmic, and histogram equalization. Adjust black point and white point with sliders or presets.
WCS Overlay
When a frame has been plate-solved, overlay catalog labels and coordinate grid directly on the image. Identify objects and verify framing.
Image Annotation
Automatically annotate solved frames with catalog objects within the field of view. Labels, markers, and coordinates rendered on the image.
Weather & Safety Monitor
Real-time weather station integration monitoring temperature, humidity, wind speed, cloud cover, and rain. Automatic park and dome closure when conditions become unsafe.
Safety Actions
When safe_to_observe becomes false: abort current exposure, stop guiding, park mount, close dome shutter. All automated.
Dome & Rotator
Full dome control with shutter open/close, azimuth tracking (follows mount position), and park. Rotator control with absolute and relative positioning.
Dome
Open/close shutter, GoTo azimuth, park. Azimuth tracking follows mount to keep the slit aligned with the telescope.
Rotator
Rotate to absolute angle, rotate relative, sync to angle, and abort. Used for camera angle alignment and framing optimization.
Dew Heater Control
Control multi-channel dew heater controllers to keep optics and guide scopes clear of dew through the night.
Manual Power
Set heater power (0-100%) per channel independently — useful for a main scope heater band and a separate guide scope band.
Auto Mode
Enable automatic control per channel; power is adjusted based on temperature and humidity readings from the connected weather station.
Switch Hub
Control powered outlet switches exposed by an INDI or ASCOM switch hub, so you can power-cycle equipment without leaving the observatory setup screen.
Switch Control
View every switch and its current state or value, then toggle boolean switches or set numeric values for variable switches — power a mount, camera, or dew heater remotely.
Session Report & OAL Export
Review a complete summary of what was actually captured once an imaging session ends.
Session Report
Per-filter sub-exposure counts, total integration time, gain/offset, sensor temperature, average HFR, guiding RMS, and moon phase for the session.
OAL Export
Export the session as an Observation Activity Log (OAL) XML file, compatible with observation-logging tools and clubs that require the OAL schema.
Cloud PublishPRO
Publish captured images to OpenSkyLab Cloud, an optional AstroBin-style sharing service for showing off and archiving your results. Requires an active Pro license (used as your Cloud account) and an internet connection — OpenSkyLab itself keeps working fully offline either way.
Auto-Filled Acquisition Data
Publishing pulls acquisition details straight from your rig profile and session: per-filter sub-exposures, total integration, gain, sensor temperature, location, date, software, average HFR, guiding RMS, and moon phase.
Visibility & Metadata
Add a title, description, and choose public or unlisted visibility before publishing an image.
On Windows, legacy ASCOM devices that only expose a COM interface (not Alpaca) can still be used with OpenSkyLab through the built-in ASCOM Bridge.
Bridge Process
Start or stop a local bridge process from Settings. It translates ASCOM COM calls to ASCOM Alpaca REST on a chosen port, so OpenSkyLab talks to it like any other Alpaca device.
Status Monitoring
View bridge status (running/stopped) and process ID directly from OpenSkyLab, without switching to a separate Windows tool.
Every panel in the UI has a ? button with inline help explaining the feature. Press F1 anywhere for context-sensitive help.
