Observability Filtering¶

AstroManager uses sophisticated observability calculations to determine when targets can be imaged from your location.

What is Observability?¶

Observability refers to whether a celestial object can be effectively imaged at a given time from your location. Factors include:

• Altitude: How high the object is above the horizon
• Azimuth: Cardinal direction
• Hour Angle: Position relative to meridian
• Sun Position: Darkness level
• Moon Position: Interference from moonlight
• Horizon Obstructions: Local obstacles

Altitude Calculations¶

Minimum Altitude¶

Set your minimum imaging altitude:

• Observatory Default: Applies to all targets
• Per-Target Override: Custom for specific objects

Common thresholds:

Why Altitude Matters¶

Lower altitudes mean:

• ❌ More atmosphere to penetrate
• ❌ Worse seeing conditions
• ❌ More light pollution
• ❌ Greater extinction (dimming)
• ❌ More atmospheric dispersion

Altitude Charts¶

The altitude chart shows:

• Object altitude over 24 hours
• Your minimum threshold line
• Imaging window (above threshold)
• Transit (highest point)

Sun Position & Darkness¶

Twilight Phases¶

Imaging Window¶

AstroManager calculates your nightly imaging window:

• Start: Astronomical twilight end
• End: Astronomical twilight begin
• Duration: Total dark hours

Moon Interference¶

Moon Position¶

AstroManager tracks:

• Current moon RA/Dec
• Angular distance to each target
• Moon altitude at each time

Moon Phase¶

Moon Avoidance Profiles¶

Configure filter-specific rules:

Example Profile: "Broadband Imaging"

Example Profile: "Narrowband"

Observable Duration¶

Calculating Duration¶

For each target, AstroManager calculates:

1. When it rises above minimum altitude
2. When it sets below minimum altitude
3. Total hours observable
4. Overlap with darkness
5. Moon interference periods

Duration Filters¶

Filter targets by:

• Minimum Hours: At least X hours observable
• Moon-Free Hours: Hours with acceptable moon
• Peak Duration: Longest single window

Seasonal Observability¶

Best Season¶

Objects have optimal viewing seasons:

• Winter Objects: Orion, Taurus, Gemini
• Spring Objects: Leo, Virgo, Coma Berenices
• Summer Objects: Cygnus, Sagittarius, Scorpius
• Autumn Objects: Andromeda, Pegasus, Cassiopeia

Long-Term Planning¶

AstroManager's Imaging Possibilities feature shows:

• Monthly observability for coming year
• Best months for each target
• Moon-free periods

Horizon Profiles¶

Custom Horizons¶

If you have local obstructions (trees, buildings, mountains):

1. Go to Settings → Observatory
2. Click "Edit Horizon"
3. Enter altitude limits per azimuth
4. Save

Horizon Format¶

Define horizon as azimuth-altitude pairs:

Azimuth: 0° (N)    Altitude: 15°
Azimuth: 45° (NE)  Altitude: 10°
Azimuth: 90° (E)   Altitude: 5°
Azimuth: 135° (SE) Altitude: 8°
...

Impact on Calculations¶

Custom horizons affect:

• Observable window calculations
• Altitude chart display
• Target scheduling decisions

Scheduler Integration¶

How Observability Affects Scheduling¶

The scheduler uses observability to:

1. Filter Candidates: Only consider observable targets
2. Score Targets: Higher altitude = higher score
3. Time Windows: Schedule during optimal periods
4. Moon Avoidance: Select appropriate filters

Real-Time Updates¶

As conditions change:

• Objects rise and set
• Moon moves across sky
• Scheduler re-evaluates continuously

Tips¶