Roll-Off-Roof Observatory → Sky Coverage & Horizon Planner

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Feature list

• Rectangular or fully custom 6-wall building footprint
• Real wall-obstruction model — ray-to-wall distance from the mount's actual position
• Parked roof modeled as its own obstruction — flat, peaked (gable), or wedge (mono-slope)
• Local terrain horizon, layered on top of wall/roof obstruction
• GEM and Alt/Az/Fork mount support with meridian-flip pier-side handling
• Automatic pointing constraints
• Full-sky coverage sweep, stretched to your building's actual width/length aspect ratio
• Up to 4 telescopes — swing-radius wall clearance and telescope-to-telescope collision checking
• Plan-view Swing Clearance diagram, to scale
• Exportable horizon profile (.hrz) — walls, roof, and terrain combined
• Save/Load, dark/light mode, Reset to Defaults

Building & Mount Position

Building width, length, wall height, and mount pivot position — height above floor, and N/S and E/W offset from the building's center. All in centimetres.

Building Shape

For anything other than a simple rectangle — angled corners, an extension, an irregular footprint — turn on "Use a custom wall shape" to describe the building as up to 6 walls, each with its own angle from North and distance from center.

Roll-Off Roof

Pick which wall the roof rolls off past and how far. Three roof shapes:

• Flat — one constant height.
• Peaked (gable) — ridge parallel to travel, tapering down to eave height on both sides.
• Wedge (mono-slope) — a single slope from low to high across the roof's full width. The most common real-world shape for a roll-off roof.

Telescopes

Telescope 1 uses the OTA length/aperture and GEM Axis / Dec Offset from above. Enable up to 3 more, each with its own axis offset (cm), lateral offset (cm), tube length (mm), and aperture (mm).

Swing Clearance

Collapsed by default. Checks each telescope's worst-case distance from the mount pivot against the nearest wall, floor, and ceiling in every direction at once — not just the current pointing. Also checks telescopes against each other (parallel cylinder model — only flags a collision where along-axis ranges overlap and lateral separation is less than the sum of aperture radii).

Sky Coverage

Same concept as the dome tool. The plot is stretched to your building's actual width/length ratio. Includes an Export as Horizon File (.hrz) button.

Telescope Pointing & 3D Preview

Same Hour Angle/Dec or Alt/Az controls, jog pad, and pier-side handling as the dome tool. The 3D view shows the actual building shape, the parked roof, cardinal directions, the celestial equator, and wireframe swing-radius spheres per telescope (red if any fails to clear).

Tips

• Run Swing Clearance early — it's a static check that only needs doing once per hardware configuration.
• The parked roof's height matters — if it's on a raised track, it can end up taller than the walls.
• Export the horizon file once your building geometry is finalised, and load it into NINA or Stellarium.