Astrophotography Planning Calculator

A fast, local, browser‑based tool for planning astrophotography sessions

About This Tool & How to Use

Inputs & Visibility Hours

The Theoretical Visibility Hours chart estimates usable hours per night across the year for your selected locations. Note: This calculation assumes perfect weather conditions and does not account for atmospheric factors.

Object: Catalog name (e.g., M31, NGC 6822, Sh2‑29), use manual coordinates, or select a planet.
Manual Coordinates: Toggle to input custom RA/Dec in decimal (10.6847h, 41.2686°) or traditional formats (10h 41m 4.5s, +41° 16' 8.4").
Planet Target: Toggle to track a planet (Mercury→Neptune + Pluto) using precise ephemerides that update per time step.
Locations: Matching comma‑separated latitudes and longitudes (negative = South/West).
Altitude threshold: Minimum target altitude (e.g., 20°).
Sun altitude threshold: Maximum Sun altitude (e.g., −15°) for darkness/twilight.
Year: Automatically uses current year for calculations.
Precision: High-precision daily sampling (31 samples per month) for smooth visualization.

Altitude Plot & Sky Path Animation

Altitude Plot shows a single night (local noon → next noon; midnight at center).

Twilight shading: Civil/nautical/astronomical; daytime is white.
Custom Horizon: Paste azimuth/altitude pairs (one per line) to draw obstructions.
Moon trace: Dashed line to compare lunar elevation.
Timezone: Time axis reflects the observing site's local time.

Sky Path Plots (below the Altitude Plot) show the target and Moon across the sky with interactive animation:

2D Polar View: Horizon = outer ring; zenith at center; N/E/S/W marked.
3D Sphere View: Upper hemisphere of the visible sky; separate section for 3D visualization.
Time Animation: Use the time slider and play/pause controls to see object movement throughout the night.
Real-time Markers: Animated markers show current position of target and Moon for any selected time.

Workflow: Choose object (catalog search, manual coordinates, or planet) → fill parameters → click Calculate → review yearly Theoretical Visibility Hours → open "Altitude Plot" and adjust date/location/horizon → use time animation to explore object movement across the sky.

Calculation Parameters

Target Object

Astronomical Object

Search from 530+ catalog objects or use manual coordinates below

Use Manual Coordinates

Use Planet

Observation Locations

Latitudes (°N)

Comma-separated latitudes (negative for Southern Hemisphere)

Longitudes (°E/W)

Comma-separated longitudes (negative for Western Hemisphere)

Tip: Use matching number of latitudes and longitudes. Examples: New York (40.7, -74.0), Tokyo (35.7, 139.7), Sydney (-33.9, 151.2)

Observation Criteria

Target Altitude Threshold (°)

Minimum target altitude above horizon (0-90°)

Sun Altitude Threshold (°)

Maximum Sun altitude for dark sky (-18° to 0°)

Calculation Year

Year for visibility calculations

Target Altitude:
• 20°: Avoid extinction
• 30°: Better quality

Sun Altitude Guide:
• -12°: Nautical twilight
• -18°: Astronomical twilight

Moon Filters (Optional)

Optional Moon Filtering: Enable one or both filters to exclude time periods when the Moon may interfere with your astrophotography. Each filter can be toggled independently based on your specific imaging requirements. When a Moon filter is enabled, any time where Moon data is unavailable is excluded from the total.

Enable Moon Altitude Filter

Enable Moon Separation Filter

Moon Altitude Guide:
• 0°: Moon below horizon (most restrictive)
• -5°: Moon well below horizon
• 15°: Low Moon interference

Moon Separation Guide:
• 30°: Recommended minimum
• 45°: Good separation
• 60°+: Optimal conditions

Calculating imaging hours... This may take a few moments.

Quality Imaging Hours Plot

Altitude Plot

Altitude Plot Parameters

Select Location

Choose from your calculation locations or use custom coordinates

Date

Latitude (°N)

Longitude (°E/W)

Elevation (m)

Custom Horizon Data (optional)

If provided, a dotted brown “Custom Horizon” line is plotted using linear interpolation. Empty = no horizon plot.

Sky Path (2D Polar View)

Note: Moon path gaps are normal - the Moon moves ~13° eastward daily, so it's in a different position after 24 hours.

Sky Path (3D Sphere View)

Note: 3D view shows the upper hemisphere of the visible sky. Use mouse to rotate. Moon path gaps are normal - the Moon moves ~13° eastward daily, so it's in a different position after 24 hours.