Sun and Moon Perimeter Orbs

The orb overlay subsystem calculates high-precision ephemeris positions for the Sun and Moon using the ephem library, projecting their positions along the perimeter border of captured images. This provides immediate visual context regarding diurnal cycles, moon phase illumination, and twilight transitions.

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1. Projection Modes

The orb calculation mode is configured under Camera Settings -> Overlay -> Orb Properties (ORB_PROPERTIES -> MODE):

Mode	Key	Description
Local Hour Angle	ha	Simulates a 24-hour diurnal clock along the rectangular image perimeter. Top-center (12:00) represents upper meridian transit (solar noon).
Azimuth	az	Projects coordinates using 360° compass bearings. By default, 0° (North) aligns with the top-center edge.
Altitude	alt	Projects coordinates vertically along the image margins (+90° to -90°). Ascending bodies appear on the right margin; descending bodies appear on the left margin.
Disabled	off	Deactivates orb calculations and perimeter renderings.

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2. Twilight and Altitude Boundary Indicators

When ha or az mode is active, indicator tick marks are plotted along the image edge to mark key solar altitude thresholds:

• 0.0° — Astronomical Horizon (Sunrise / Sunset)
• -6.0° — Civil Dawn / Dusk
• -12.0° — Nautical Dawn / Dusk
• -18.0° — Astronomical Dawn / Dusk

The larger, accented tick mark (rendered in the primary text color) indicates the configured Night Sun Altitude (NIGHT_SUN_ALTITUDE, typically -6°). This boundary marks the exact threshold where indi-allsky transitions between daytime auto-exposure routines and nighttime long-exposure sequences.

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3. Configuration Parameters

In the web interface under Configuration -> Overlays -> Orb Properties, or via JSON configuration:

"ORB_PROPERTIES": {
    "MODE": "ha",
    "RADIUS": 9,
    "SUN_COLOR": [200, 200, 0],
    "MOON_COLOR": [128, 128, 128],
    "AZ_OFFSET": 0.0,
    "RETROGRADE": false
}

• MODE: Selects ha (Hour Angle), az (Azimuth), alt (Altitude), or off.
• RADIUS: Integer pixel radius for the rendered celestial circles (default: 9).
• SUN_COLOR: RGB array defining the rendered solar marker color (default: [200, 200, 0], yellow).
• MOON_COLOR: RGB array defining the rendered lunar marker color (default: [128, 128, 128], neutral grey).
• AZ_OFFSET: Float value in degrees to compensate for physical camera rotational misalignment relative to true North. Valid for ha and az modes.
• RETROGRADE: Boolean flag (true / false). When optical paths incorporate mirrored surfaces or software image inversions (flip horizontal/vertical), set to true to invert orb travel along the perimeter.