Help & catalog guide
Observing modes, moon selections, and 3D Sim architecture
Amateur and Pro
These are the two observing modes. Signed-in users can choose moons independently for each mode in Settings → Celestial Objects. Pro is stored internally as expert. The existing selectable moons and your saved selections are unchanged; difficult targets remain selectable. A selection is not a guarantee that a moon is observable with your equipment or at the current time. Former Explore-mode preferences now use Pro.
3D Sim: a separate educational view
The 3D Sim has its own object selection, independent of Amateur and Pro. Open Explore objects and use any group checkbox to show or hide its available members; a partially checked box means only some are selected. The camera frames the selected objects. Click an object name to focus on it. Selection is remembered for this browser tab’s session, including tab changes and reloads, but is not saved to your account.
Why some moons are greyed out
Rows marked “3D Sim only” are descriptive catalog entries for additional moons modeled in the simulation. Their Amateur and Pro controls are disabled. This is an app-coverage distinction, not a claim that they are physically impossible to observe from Earth. Existing Tracker moons retain their selection controls. Earth’s Moon has its own dedicated view.
moon_catalog — the reference roster
Stores planet and moon identifiers, display order, default visibility for both observing modes, and descriptive observing notes such as magnitude and suggested aperture. selectable_amateur_pro distinguishes selectable Tracker moons from read-only 3D Sim additions. It does not drive the simulation’s object definitions or orbital physics.
user_moon_visibility — your observing choices
Stores a visible flag for each signed-in user, observing mode, planet and selectable moon. Missing choices start from the catalog defaults without overwriting existing preferences. The app returns only the current user’s choices. This table does not store 3D Sim object selections.
Physics, source data and precision
Stable simulation objects and analytical orbital models live in structured, versioned source code for fast startup and reproducibility. Cached JPL geometric vectors and orbital elements supplement those models where supported; missing or invalid data is labeled or hidden rather than shown as a valid position. Orbit paths are subtle and remain visible for selected, available bodies. Display sizes and distances are educational, not a single physical scale. Use the Tracker and JPL Horizons for observation work; Catalog references in Resources links to NASA and JPL source material.