Features
Grouped by what you're trying to do, not by screen name. free & open source marks what is never behind a paywall; paid candidate marks what the Offers page prices; never sold marks what the project will never charge for, on principle.
Observation planner
core free & open source
Combine a date, a known location and an equipment profile with target recommendations, altitude curves, an editable schedule and a short-range astronomy-weather summary. A local, searchable deep-sky catalogue (imported from OpenNGC) comes with curated Essential and Extended target lists. Plan locally as a guest, or sign in for a plan the portal keeps for you.
Multiple local plans and advanced local planning tools are the Advanced Planning one-time purchase — see Offers. The plan itself always stays correct: a horizon mask, a minimum altitude, lunar separation and mount-safety restrictions are never sold.
Framings and mosaics
core free & open source
Save a framing from the sky map, reuse it across plans, and export it for the field (including an ASIAIR target list). Mosaic framings and advanced constraints are part of Advanced Planning; a simple framing always stays free.
Night in progress
free & open source
An in-field screen for the plan you're actually running tonight: a timeline showing where the night should be, one tap to start, finish or skip a target, quick time retouches, and every target as a rich card with its description. A red night-vision mode is on by default, and the current target's description can be read aloud through the phone's own offline speech engine.
On iOS, a Live Activity on the lock screen and in the Dynamic Island shows the current target and the session status without unlocking the phone; on Android, a persistent notification plays the same role.
Debriefing
free & open source
A plan is an intention; a session is what actually happened. After the night, a short debriefing — executed, partial, or abandoned — turns the plan into a session record, target by target, with an optional note. Field edits made after the portal already has a debrief are never silently discarded: they come back as a supplement to review.
Synchronization
Pair a device to a portal once; from then on, plans, sessions and debriefings can move between your phone and the web. Two devices editing the same plan offline both keep their edits — resolving a conflict is always one explicit action, never silent.
A free account gets one synchronized plan, as a sample of the paid value. Multiple synchronized plans, a private capture gallery and processed-image uploads are the Synchronization subscription; local night analysis (log-derived quality and guiding graphs, automatic progressions) is Advanced Synchronization. See Offers for what each level includes.
Offline
never a paid feature
The app starts and stays usable with no network at all: guest mode makes no private or sync call, and every public read carries an explicit cached/offline state instead of a spinner that never resolves. A base pack (catalogue index, a compact light-pollution raster) downloads automatically on first launch; optional sky-imagery tiers (Essential through Quality) are a storage choice, not a purchase — sky imagery itself is never sold.
Night mode
free & open source
A dedicated red night-vision theme keeps your eyes dark-adapted in the field, alongside the app's own dark-by-default interface everywhere else.
Self-hosted sky quality
free & open source
A per-place Bortle/SQM estimate is computed from the portal's own satellite data — no third-party map service, no outbound request at request time. It includes a regional calibration fitted against real measurements where they exist: see Calibrating the sky background for Japan for the method and the numbers behind it.