Arcsecond.local on your network
Arcsecond.local listens on one port of your local network (5555) and on nothing from the Internet side. Everything else is outbound. One destination is required: licensing.arcsecond.io on port 443. A default installation also looks up 10 public astronomy services, all on port 443, and runs without them. The rest exists only when you turn a feature on.
What listens
- Port 5555, every interface: The application itself.
- Port 8800, this machine only: The programming interface, for the arcsecond command and scripts run on the machine itself.
- Port 8765, every interface: Relays webcam and all-sky camera images to the installation. Runs only when cameras are registered. Optional.
What it contacts
Required. Outbound, encrypted.
| Destination | Port | What for |
|---|---|---|
| licensing.arcsecond.io | 443 | Licence activation and daily check |
Public catalogues and lookups. Outbound, encrypted. The installation runs without them, with less to show.
| Destination | Port | What for |
|---|---|---|
| exoplanetarchive.ipac.caltech.edu | 443 | Exoplanets and transits (NASA archive) |
| ogle.astrouw.edu.pl | 443 | Microlensing candidates (OGLE) |
| minorplanetcenter.net, cgi.minorplanetcenter.net | 443 | Near-Earth object candidates |
| celestrak.org | 443 | Satellite orbits |
| simbad.cds.unistra.fr | 443 | Object names and coordinates (SIMBAD) |
| timezonedb.com | 443 | Time-zone table refresh |
| statics.arcsecond.io | 443 | Sky darkness of a site |
| ssd.jpl.nasa.gov, ssd-api.jpl.nasa.gov | 443 | Comet and asteroid positions |
| skyview.gsfc.nasa.gov | 443 | Finding charts (NASA SkyView) |
| datacenter.iers.org, maia.usno.navy.mil, hpiers.obspm.fr, data.iana.org | 443 | Earth rotation tables |
Only when you turn the feature on. Outbound. Nothing here is contacted by a default installation.
| Destination | Port | What for |
|---|---|---|
| scixplorer.org | 443 | Papers about a target |
| auth.gcn.nasa.gov | 443 | Transient alerts: sign-in |
| kafka, kafka1, kafka2, kafka3 .gcn.nasa.gov | 9092 | Transient alerts: the feed |
| api.tomorrow.io | 443 | Weather forecast |
| www.wis-tns.org | 443 | Transient Name Server lookups |
| a server you choose | 445, 22, 21 or 443 | Copies to a storage you attach |
| a server you choose | 587, 465 or 25 | Email through your mail server |
To install and to update. Outbound, encrypted. Not needed while running.
| Destination | Port | What for |
|---|---|---|
| ghcr.io, pkg-containers.githubusercontent.com | 443 | Arcsecond.local itself |
| registry-1.docker.io, auth.docker.io, production.cloudflare.docker.com | 443 | Database and message broker |
| pypi.org, files.pythonhosted.org | 443 | The arcsecond command |
From your users' browsers. Outbound, encrypted, from their workstations, not from the installation.
| Destination | Port | What for |
|---|---|---|
| server.arcgisonline.com, tile.openstreetmap.org, global.ssl.fastly.net, api.maptiler.com | 443 | Map backgrounds |
| alasky.cds.unistra.fr, alaskybis.cds.unistra.fr, alasky.unistra.fr, skyview.gsfc.nasa.gov | 443 | Sky survey pictures |
| statics.arcsecond.io | 443 | Light-pollution layer, illustrations |
On your local network only. Never leaves the site.
| Destination | Port | What for |
|---|---|---|
| addresses you enter | set per device | Telescopes, domes, cameras, weather |
| a broadcast on your network | 32227 (datagram) | Finding instruments on the network |
| addresses you enter | 554, 80 or 443 | Webcams and all-sky cameras |
What never leaves the site
- Images and data files
- Night logs, sessions and observing conditions
- Equipment configuration and instrument state
- Accounts, passwords and access keys of the installation's users
- Usage statistics, error reports or any other telemetry
If the connection is cut
An activated installation keeps operating with no outside connection at all: instrument control and data recording are local. It only does without the lookups listed above.
Check it yourself
- Run
arcsecond doctoron the machine: it tests every destination above and sends nothing about your observatory.arcsecond doctor --reportwrites the result to a file for your records. - This sheet is generated from the software's own network manifest (audited 2026-10-05); the current version is at docs.arcsecond.io/reference/network.
- Security questions: team@arcsecond.io
To print, and to paste
- The same sheet as a one-page PDF.
- The same sheet on one printable page, to print from your browser.
- The request to send to whoever runs your firewall, as plain text.