Appendix D — Frequently Asked Questions
The questions that come up a lot, with short answers and pointers into the chapters that go deeper. For failure symptoms and diagnostics, see Appendix C.
D.1 General
Is Polaris a N.I.N.A. replacement? No. It is a community fork built specifically for headless operation (Linux, Raspberry Pi, or a Windows mini-PC without a display). The original N.I.N.A. at nighttime-imaging.eu is a full Windows desktop application and remains the gold standard on that platform (Berg and the N.I.N.A. contributors, n.d.); Polaris targets the remote-site and single-board- computer use cases it does not (Chapter 1).
Does Polaris share code with N.I.N.A.? Some, but heavily forked. The Windows-only WPF UI layer is gone, replaced by ASP.NET Core and Alpine.js. Core libraries (the FITS reader, star detection, plate solving) retain N.I.N.A. heritage but have diverged. The license remains MPL 2.0.
Will my N.I.N.A. sequences work? There is no automatic import. The Advanced Sequencer’s JSON format is similar but not bit-compatible; rebuilding sequences in the ADV tab is the right path, and it does not take long for typical multi-target plans (Chapter 15).
D.2 Hardware
What cameras work? Any camera with an INDI driver (most ZWO, QHY, Atik, ToupTek, ToupSky, Altair, and gphoto-supported DSLRs, among others), Alpaca cameras on Windows, and DSLR or mirrorless bodies through the vendor SDKs (Canon EDSDK, Nikon Imaging SDK, Sony Camera Remote SDK 2). The driver dropdown on the camera card in RIGS shows what Polaris detected on your host (Chapter 5, Chapter 6).
What mounts work? Via INDI: EQMod (CGEM, EQ6, AVX, HEQ5, Atlas), Celestron NexStar, iOptron, Sky-Watcher, and LX200. Via Alpaca: anything with an ASCOM driver. Via direct WiFi: SynScan, NexStar, and LX200 over TCP (Chapter 7).
Raspberry Pi 4 or 5? A Pi 4 with 4 GB or more handles capture and live stacking fine. The Pi 5 is faster for planetary processing and the xpra-embedded PHD2 GUI (about three times faster xpra rendering). A Pi 3 is too slow for live stacking. The full sizing table is in Appendix A.
Can Polaris and the equipment be on different machines? Yes: INDI can run on a Pi at the telescope while Polaris runs elsewhere; set Indi:Host in appsettings.json to the remote Pi’s address (Chapter 31). But this is fragile, because USB drivers want to be physically next to the camera; the reference deployment is Polaris and INDI together on the same computer at the telescope.
I need the INDI control panel but my Pi OS no longer packages it. Use the built-in INDI control panel sub-tab in RIGS. It is a full in-browser property browser (read and edit every device property, auto-saved to the driver configuration), so the standalone Qt application, which recent Pi OS and libindi 2.x releases no longer ship, is not needed. Each property also has a (?) help icon: hover for a plain-language description, click to write your own note (Chapter 5).
D.3 Workflow
AUTORUN or ADV, which should I use? AUTORUN for “shoot 100 frames of M81 in L tonight”. ADV for “M81 in LRGB, with auto-flip, dither every 3 frames, and a safety abort on cloud cover”. See Chapter 14 and Chapter 15.
Can I edit a sequence while it runs? In AUTORUN, in a limited way: pause, edit, resume. In ADV the same, with the caveat that some container types lock their children during execution.
Do I have to focus before every sequence? The first time each night, yes. After that, enable auto-focus triggers (in ADV) or the LIVE tab’s auto-refocus, and Polaris refocuses automatically on temperature change, HFR degradation, elapsed time, or frame count (Chapter 11, Chapter 17).
What is the difference between LIVE auto-recenter and the ADV “Center After Drift” trigger? LIVE’s recenter is scoped to the live stack: it uses the first frame’s plate solve as its reference and can solve every frame if the drift threshold is enabled. ADV’s trigger fires within a sequence between exposures and uses the target’s intended (RA, Dec) as the reference. They serve different workflows; both are equally valid (Chapter 17, Chapter 15).
D.4 Storage
How much disk does a typical session take? Deep-sky capture: 30-50 MB per FITS frame, so 200 frames is 6-10 GB. Planetary: 1.5-3 GB per 60-second SER video. Calibration masters are trivial. Plan for 50+ GB free for a full night (Chapter 19).
Can I store to a network share or NAS? Yes: in the FILES tab, navigate to the mount point (for example /mnt/nas/astro/) and click Set as Studio root. Writing frames is slightly slower over the network than to a local SSD; live stacking is unaffected because it accumulates in memory (Chapter 19).
Where are my profiles stored? In profile.json under the per-user application data folder: %LocalAppData%\Polaris\ on Windows, ~/.config/polaris/ on Linux. Back it up before major OS upgrades; losing it loses your rig configurations (Chapter 28).
How do I wipe all my settings, say before sharing an SD card? In SETTINGS, use Reset everything to factory defaults. It clears every profile and rig, the app password and login sessions, the observer location, and the browser’s UI preferences, then reloads into first-run state. Captured images and FITS files are kept. It cannot be undone, so back up the profile first if you might want it later (Chapter 28).
D.5 Software
Why .NET 10? A faster runtime, better cross-platform performance, first-class async support, and native ARM64 publishing. .NET 8 LTS would work too; the project tracks the latest short-term-support release for performance (Chapter 30).
Why ASP.NET Core and Alpine.js instead of React or Vue? Server-side rendering of the HTML plus a minimal JavaScript framework keeps the download tiny (about 150 KB before the WebGL2 shaders), first paint fast on mobile, and the contributor experience free of any build pipeline. Alpine.js provides reactivity without the complexity of a bundler. The trade-off is less suitability for a complex single-page app, but Polaris is a multi-tab dashboard, not a CRUD app (Chapter 30).
How do I see live logs? The server logs to standard output; run it from a terminal to watch. Set Logging:LogLevel:Default to "Debug" in appsettings.json for verbose output. The LOG panel in the UI collects server logs, HTTP traffic, and browser errors into one exportable stream (Chapter 28).
Can I write plugins? There is a plugin system (Services/Plugins/PluginLoaderService.cs) that loads MEF-exported types (MEF is .NET’s built-in extension loader) from the plugins/ folder at startup. The specification is loose right now; if you want to write one, open an issue and the project will help you bootstrap (Chapter 32).
D.6 Network
I am at a dark site with no internet. Does Polaris work? Yes. The sky catalog, the map engine, and the DSO database are all offline (the bundled sky tiles cover stars to at least magnitude 12, deep-sky surveys, constellations, and the Milky Way). Plate solving via ASTAP is offline, and PHD2 and INDI are local. The only internet-dependent feature is the Tonight’s Best image fetcher, which pulls NASA and Wikipedia thumbnails and simply shows placeholders offline (Chapter 10, Appendix A).
Can multiple browsers connect to the same Polaris? Yes. Each browser gets its own WebSocket streams, and state lives on the server, so all clients see the same view. Useful for showing an astrophotography buddy what the rig is seeing (Chapter 1).
D.7 On the images themselves
Polaris detects 0 stars on focused frames. The exposure is too short or the sky is too bright (twilight). Bump the exposure to 5 s or more and try again at full astronomical darkness.
HFR jumps by 30% after a meridian flip. That is not normal, is it? It can be. The pier-side change rotates the field; star detection sees “new” stars and the median shifts temporarily. If it persists more than 3-5 frames, something else (collimation, dew, flexure) is wrong.
Plate solving uses ASTAP, but I have Astrometry.net set up. Can I use it? Yes: in SETTINGS, under Plate solver, set the primary solver to Astrometry.net local. You need solve-field on the PATH and the matching index files (Appendix A).
How accurate is the dithering? PHD2’s dither is sub-pixel accurate; Polaris just triggers it and waits for settling. The dither amount you configure is in guide- camera pixels; how far the main camera moves depends on the ratio of guide to main focal lengths (Chapter 12).