Lab build — planning for more than one telescope.
Being tried out here before it goes into the released calculator, so expect rough edges:
the extra telescopes are drawn as a swept sphere rather than a modelled pier, the setup check
still describes telescope 1 alone, and no telescope blocks another’s view in the sky
coverage.What this changes →Released calculator →
Walls — solid up to wall height, the building's actual footprint
Parked roof box — the rolled-off roof's obstruction, past whichever wall it slides beyond
Usable roof space (blue) — the room above the wall top that the roof structure leaves; it follows the pitch, so it tapers to nothing at the eaves. Zero for a standard truss
N / E / S / W — cardinal directions at the walls
Small bar — OTA
Amber line — optical axis
Rust-colored skyline — your local (terrain) horizon limit
Blue arc — the celestial equator (Dec=0); genuinely tilts with latitude, crossing the horizon due East and due West
Bright dot — the elevated celestial pole, at altitude = your latitude — where a polar-aligned GEM's RA axis points
Drag to orbit · scroll to zoom
Telescope Pointing
Drives the live obstruction calculation, 3D preview, and sky coverage sweep. With two telescopes, the toggle below picks which one these controls slew.
the sliders below drive the OTA you pick — the other one holds the pointing you left it at, and every pointing check describes the one you are slewing
°
°
°
°
°
AP park
JOG
Step size
Hold to keep jogging. Nudges whichever pointing mode is active above.
RA
Dec
Alt
Az
✓Valid pointing — clear of the walls, roof, and local horizon.
Sky Coverage
Reading this
Center = zenith, edge = horizon, up = North, right = East. The outer boundary traces your building's actual wall shape — a 4-wall rectangle shows as a rectangle, a 6-wall polygon shows its true footprint. Updates live as you change your setup.
● Green — clear of walls, roof, and horizon ● Red — blocked by a wall or the parked roof ● Brown — below your local (terrain) horizon
⚠ Mount position falls outside the building footprint — check your offset measurements.
⚠ Pointing was pulled up to clear the walls/roof/horizon at this azimuth.
⚠ Declination was raised to the lowest value ever observable from this latitude (lat − 90°) — anything below that never clears the horizon, at any hour angle.
Building & Roof
Building & Mount Position
Measured from the building's true geometric center on the floor (not magnetic north). Positive North offset means the mount is closer to the North wall.
cm
cm
cm
cm
Measure from each wall to directly below the mount's RA/Dec pivot on the floor.
cm
cm
cm
cm
N/S offset: · + = North of center
E/W offset: · + = East of center
Building Shape
Most buildings are a simple rectangle — the width/length above cover that. Non-rectangular buildings (angled corners, an extension, an irregular footprint) can be described directly as up to 6 walls, each its own distance and angle from center.
Roll-Off Roof
The roof rolls off past one wall and parks there — that parked structure is its own obstruction, not just an open gap.
how far the roof slides past that wall
cm
Optical Axis & Mount
Optical Axis Offset
Mount type changes the OTA's swing in the 3D preview and how pier side affects it. Doesn't change the wall/roof obstruction math itself — that's driven purely by true Alt/Az.
Pier and mount head — how high the RA/Dec pivot sits, and how thick the pier is.
floor to top of pier flange
in
in
pier flange to RA/Dec pivot
in
Optical System
Used for the 3D preview and obstruction check. OTA fields always in mm.
mm
mm
tube body including rings — 0 estimates it from the aperture
mm
adds to the tube length; drawn in a lighter tone
mm
centre of tube + shield relative to the Dec axis; + = toward the aperture
mm
RA axis to the far end of the shaft — 0 if you run without one
mm
Telescope 1
positive = North of center
cm
positive = East of center
cm
cm
Mount type and OTA dimensions come from Step 3 above. The Step 1 N/S, E/W, and height fields separately drive the live pointing preview and 3D scene.
the smallest gap allowed between two telescopes' swept spheres, measured centre to centre in three dimensions — so a difference in mount height counts toward it
cm
Sky Coverage
Sky Coverage
Sweeps a grid across the whole sky and checks whether each point clears the walls, the parked roof, and your local horizon — not a dome shutter, since a roll-off roof either fully opens or fully closes.
Mount System
Pick your mount to fill in its geometry, or leave it on Generic and enter your own.