Nebulink User Manual
Welcome
Nebulink runs on your Windows PC and controls your ZWO Seestar smart telescopes over your home Wi-Fi. It shows live status and sky conditions, points the scope from a star chart, runs a whole night's imaging plan unattended, and gathers your pictures in one album.
Nebulink works with the Seestar S50 Pro and the Seestar S30, and you can connect several scopes at once. It is an independent product and isn't made by ZWO.
What you need
- A Windows PC on the same Wi-Fi network as your telescopes
- Python 3.8 or later
- Each Seestar set to Station Mode (joined to your home Wi-Fi) in the Seestar app
- Each scope's network address, for example 192.168.1.85, shown in the Seestar app under station-mode settings
- An internet connection on the PC for the weather forecast and sky photos (everything else works offline)
Installation and first run
Setup takes about ten minutes and is done once. After that, starting Nebulink is one command.
- Unzip nebulink.zip into a folder, for example
Downloads\nebulink. - Open PowerShell in that folder and install the helper libraries:
pip install seestarpy opencv-python numpy - Set up the connection key. Seestar firmware 7.18 and later only accepts commands from authenticated apps. Download the official Seestar Android app file (APK), save it in the folder, and run:
python -m seestarpy.extract_pem .\<apk file name>.apk
The key is saved toC:\Users\<you>\.seestarpy\seestar.pem. Keep it private. - Close the Seestar app on your phone, then start Nebulink with your scopes' addresses:
python app.py 192.168.1.85 192.168.1.126 - Your browser opens at http://127.0.0.1:8050. If it doesn't, type that address yourself.
Leave the PowerShell window open while you use Nebulink; closing it stops the app. Press Ctrl+C in that window to quit.
Try it without a telescope: run python app.py --demo to explore every page with simulated scopes.
Adding a scope later: type its address on the Overview page under Seestar address and press Connect.
Getting around
Every page shares the same frame: the header and status bar across the top, the page list on the left, and the copyright line at the bottom.
Header. Shows a greeting, when full darkness starts or ends tonight, the time, and the Night mode button. Night mode turns the whole app dim red so your eyes stay adapted to the dark; press it again to switch back.
Status bar. Always shows the selected scope at a glance:
| Item | What it tells you |
|---|---|
| Seestar | The model, such as S50 Pro |
| Connection | Green dot = connected, red = unreachable, plus its address |
| Activity | Stacking, GoTo, Slewing, Focusing, Parked or Idle, and the target |
| Tracking | Whether the mount is following the sky |
| Filter | IR-cut or LP |
| Temp | Outside air temperature and the scope's own temperature, in °F |
| Battery | Charge level, and whether it's charging |
Two buttons sit at the right of the status bar. Stop halts any movement at once; it turns red and reads Stop GoTo while the scope is slewing. Power off Seestar shuts the scope down after a confirmation. Once off, it can only be turned on again with its power button.
Pages. Overview, Live view, Star chart, Alignment, Stacking, Planner, Album, Manual and About. If you have more than one scope, pick which one you're working with on the Overview page; every page follows that choice.
Overview
The Overview page answers "how is the scope doing, and how is tonight looking?" on one screen. It refreshes every couple of seconds.
| Card | What it shows |
|---|---|
| My telescope | Model, online status, battery, firmware, temperature and Wi-Fi signal. Buttons switch between scopes; the address box connects a new one. |
| Current target | A sky survey photo of where the scope is pointing, with a box showing its field of view, plus exposure progress, tracking, filter and mode. |
| Live stack | The stacked picture as it builds, frames accepted and rejected, total exposure time, Auto DBE and autofocus. |
| Your night | The six best showpiece targets from your location tonight, ranked by hours above 30° in full darkness. The one you're imaging is highlighted. |
| Conditions | An hour-by-hour cloud chart from 6 pm to 6 am, the best clear window, temperature, wind, humidity, dew risk and whether the dew heater is on. |
| Sun & Moon | When astronomical darkness starts and ends, the moon's phase, and moonrise and moonset. |
| Storage | Free space on the scope. |
| Live events | The scope's own status messages; click the heading to expand. |
The forecast and sky photos need internet on the PC. Press the refresh button on the Conditions card to reload the forecast.
Live view
Live view shows what the scope sees and lets you move and focus it by hand.
Choose a picture. Pick a source and a camera at the top of the viewer:
- Stacked: the running stack, refreshed every 10 seconds
- Single frame: the latest individual exposure
- Video: a live video stream. The Seestar only streams video in Landscape and Solar System modes, so use Stacked or Single frame for deep sky.
- Telescope or Wide-angle: the main camera or the wide-field camera
Move the scope. Hold an arrow to move; let go to stop. The big STOP button halts movement immediately. On the keyboard, the arrow keys move and the Space bar stops. Choose a speed from Slow (¼° per second) to Max (6° per second). Each move command only lasts one second, so the scope stops on its own if the connection drops.
Focus. The focus box shows the current focuser position. Start autofocus lets the scope focus itself on stars, which takes a minute or two. The −50, −10, +10 and +50 buttons nudge focus by hand.
Save photos and video. Save photo saves a full-resolution PNG, plus a 16-bit TIFF of deep-sky images for processing in programs like Siril or PixInsight. Record video records the video stream to MP4. Files go to the captures folder next to app.py and also appear on the Album page under Saved on this PC.
If the scope is busy. Moving or focusing while the scope is stacking asks you to confirm first. If you go ahead, the stack ends cleanly and the frames so far are kept.
Star chart
The Star chart shows tonight's sky over your location, using the position your scope reports, and lets you send the scope anywhere with one click.
What's on the chart. About 5,000 stars in their true colours, constellation lines and names, the Milky Way, all 110 Messier objects and 26 popular NGC and IC targets, the planets, the Moon with its current phase, and the Sun. Targets in tonight's plan are highlighted in cyan. A green reticle and box show where your scope points and its field of view.
Look around.
- Drag to pan; scroll or pinch to zoom
- N, E, S, W and Overhead jump to that direction
- Find scope centres the chart on where the scope is pointing
- The time slider previews the sky up to 12 hours ahead; Now returns to the present
- The Show checkboxes turn layers on and off, including an altitude-azimuth grid
Find a target. Type a name in the search box (M31, Orion Nebula, Vega, Saturn) or click any object. The panel shows its type, brightness, size, position, current altitude, rise and set times, and when it's highest tonight.
GoTo. Press GoTo & start imaging. The scope slews, plate-solves to centre the target, and starts stacking if stack after GoTo is on in the Seestar app. Tick the light-pollution filter box for emission nebulae.
Safety limits. GoTo is blocked for targets below 15° and for the Sun. For the Moon and planets, use the Seestar app's Solar System mode, which uses suitable exposure settings.
Alignment
The Alignment page helps you level the tripod, check the mount, park the scope, and set up equatorial (EQ) mode.
Level the tripod. While the page is open, the dial reads the scope's tilt sensor about once a second. The edge of the dial is 5° of tilt. Adjust the tripod legs until the dot sits in the small green circle; the dot turns green below 1°. Watch which way it moves as you adjust to learn which leg to raise. A level tripod improves GoTo and tracking accuracy, even in normal Alt-Az mode.
Mount status. Shows the mount mode (Alt-Az or EQ), whether the arm is open or folded, tracking, compass heading and location. The compass is only approximate until it's calibrated in the Seestar app.
Park. Park & fold the arm moves the scope to its home position and folds it down. Make sure nothing is in the way.
EQ mode. The page shows the numbers for your location: set the wedge to your latitude (for example, 42.7° in upstate New York) and point it at true north. Switch to EQ mode stays locked until you tick the box confirming the scope is on a wedge, set to that angle, facing north, with room for the arm to swing. Switching stops imaging and swings the arm to the EQ home position.
Polar alignment measurement is not available yet.
Stacking
The Stacking page is where you choose the filter, start and stop live stacking, and watch the picture build.
Filter. Press IR-cut or LP filter; the one in use is highlighted.
| Filter | Best for |
|---|---|
| IR-cut | Galaxies, star clusters and reflection nebulae (natural colour) |
| LP (Hα + OIII) | Emission nebulae and supernova remnants; also cuts light pollution |
Nebulink looks up your current target, recommends a filter, and warns you if the other one is in place.
Live stacking. Shows the stack's state, frames accepted and rejected, total exposure time, and a progress bar for the current exposure.
- Start live stacking begins stacking on the current target
- Stop stacking ends it after a confirmation; the frames so far are kept and the scope saves the result
- Restart stack from zero throws the current stack away and starts again
Live stack result. A large view of the stacked picture, updated every 10 seconds, labelled with the target, frame count and total time. When stacking stops, the last picture stays on screen. Save stack writes a full-resolution PNG and a 16-bit TIFF to the captures folder.
Current target. Name, type, coordinates, current altitude and time on target, with a shortcut to the Star chart to pick something new.
Planner
The Planner lets you line up a night of targets and leave Nebulink to image them one after another while you sleep.
1. Choose a target. Type a name in Object name (for example M31, NGC 7000 or Orion) and pick it from the list. Then set:
- Duration in minutes
- Exposure: 10, 20 or 30 seconds per frame; 60 seconds needs EQ mode
- Filter: chosen for you based on the target type; change it if you like
The advice panel explains the target's size compared with your field of view, when it's above 30° tonight, the best filter, a suggested imaging time, and how far it is from the Moon.
2. Check the framing. The sky map shows a survey photo with a blue box for your scope's field of view.
- Drag the map to frame the target off-centre; the plan points at the box's centre
- Use − and + to zoom, ↺ and ↻ to rotate the box, and Center on object to reset
- Click another object on the map to switch to it
- The dashed green box shows where the scope points now; GoTo this framing now sends it there
Rotation is for planning only. In Alt-Az mode the field turns slowly during the night and the scope can't set its camera angle.
3. Add it to the plan. Press Add to plan. Each target in the queue shows its estimated time slot and altitude. Red means it will be too low and will be skipped; outside darkness means the slot falls in twilight. Use ↑ ↓ to reorder, ⌖ to reopen its framing, and ✕ to remove it.
4. Start the plan. Choose As soon as I press Start or a start time; the time defaults to when full darkness begins. Leave Park the scope after the last target and Stop at dawn ticked unless you have a reason not to. Press Start plan and confirm.
For each target, Nebulink then:
- Checks the target is at least 15° up, and skips it if not
- Sets the filter and exposure
- Sends the GoTo; the scope plate-solves and focuses
- Stacks for your chosen time, then stops and moves on
If the scope hasn't started stacking within 8 minutes, Nebulink moves on to the next target. At dawn the plan ends; after the last target the scope parks.
Watch or stop it. The status line and activity log show progress, and you can switch to other pages while it runs. Stop plan ends the current stack, keeps the frames already taken, and leaves unfinished targets in the queue. Reset finished marks every target as not yet imaged so you can run the plan again.
Keep the PC running. The plan runs on your PC. Keep the PC on and Nebulink open; the screen can turn off, and Nebulink stops Windows from going to sleep while a plan runs. The queue is saved, so it survives closing the app.
Album
The Album lets you browse, preview and download your pictures. It only reads files; nothing on the scope is ever changed or deleted.
On the Seestar. Press Load images. Nebulink opens the scope's shared folder (normally \\<scope address>\EMMC Images\MyWorks) and lists your target folders, newest first. Each target usually has two folders: one with the stacked results and one ending in _sub with the individual frames.
- Click a folder to open it; use the folder buttons or Parent folder to go back
- Show narrows the list to images, FITS files or videos; long folders show 48 files per page
- Click a file for a large preview; use the arrow keys or ‹ › to step through, and Esc to close
- Download saves the original file to your PC
FITS files are previewed too: Nebulink converts and brightens them so you can check individual frames without other software. Videos can be downloaded but not previewed.
Saved on this PC. This tab shows the photos and videos you saved from Live view and Stacking.
Setting the folder by hand. If Nebulink can't find the scope's files, open Folder under the buttons, paste the folder path, and press Use this folder. Find automatically searches again.
Troubleshooting
Most problems come down to the network, the connection key, or the Seestar app holding the scope. Start with the row that matches what you see.
| What you see | What to do |
|---|---|
| Status bar says Unreachable | Check the scope is on and in Station Mode, and that its address hasn't changed (see the Seestar app or your router). Close the Seestar app on your phone. |
| The scope shows status but ignores commands | The connection key is missing or doesn't match the firmware. Repeat step 3 of Installation with the newest Seestar APK. |
| The browser can't connect to 127.0.0.1:8050 | Nebulink isn't running. Start it again from PowerShell and keep that window open. |
| "seestarpy isn't installed" or "Live view needs OpenCV" | Run pip install seestarpy opencv-python numpy, then restart Nebulink. |
| No weather or sky photos | The PC needs internet for these. Press refresh on the Conditions card. |
| Live view says No video | Video only streams in the Seestar's Landscape and Solar System modes. Use Stacked or Single frame. |
| No stacked image yet | The scope isn't stacking. Start a stack, or switch to Single frame. |
| GoTo button is greyed out | The target is below 15°, or it's the Sun, Moon or a planet. The message under the button says which. |
| A plan target was skipped | It was too low when its turn came. Move it later in the queue or pick a higher target. |
| Album can't find the files | In File Explorer, type \\ followed by the scope's address. If a folder appears, paste its path into the Album's Folder box. If Windows refuses, it may be blocking guest network access; check Windows' SMB guest-logon setting. |
| The interface is too bright at night | Press Night mode in the header. |
Safety, credits and copyright
Safety
- Never point a Seestar at the Sun without its solar filter fitted. Nebulink blocks GoTo to the Sun.
- Make sure the arm has room to move before a GoTo, park, or switch to EQ mode.
- Unattended plans park the scope at the end and stop at dawn. Cover or bring the scope in if rain or heavy dew is forecast.
- Power off can only be undone with the scope's power button.
Credits. Nebulink uses seestarpy for the telescope connection, star and constellation data from d3-celestial © Olaf Frohn (BSD licence), DSS2 sky survey images via the CDS hips2fits service, weather forecasts from Open-Meteo, and OpenCV and NumPy for image processing.
Trademarks. Seestar and ZWO are trademarks of Suzhou ZWO Co., Ltd. Nebulink is an independent product and isn't affiliated with or endorsed by ZWO.
Contact. Paul R. Smaglik · psmaglik@gmail.com
© 2026 Paul R. Smaglik. All rights reserved.