Yes. Both calculators are free to use, and the source code is open under the Mozilla Public License 2.0.
No. Both tools run entirely in your browser. No installation, no account, no internet connection required after the page first loads (other than the initial Three.js CDN fetch, which is a ~600 KB file).
Not automatically. Use Save Setup to export your configuration as a JSON file, then Load Setup to restore it. Both work entirely locally.
The dome-azimuth math is ported from NINA's DomeSynchronization.cs. The field names and sign conventions in the Options → Dome tab have been stable across NINA 2.x and 3.x. If you're on an older or newer build and see unexpected behaviour, check that the field layout in NINA's Dome tab matches what the calculator describes.
The most common causes: (1) the mount's RA/Dec pivot height was measured to the wrong point — it should be the true intersection of the RA and Dec axes; (2) the N/S or E/W sign is inverted — try flipping the sign of the offset that's largest; (3) the dome radius is to the inner surface of the shell, not to the outer edge or the track.
The most common cause is the OTA aperture being set wider than the shutter. The shutter check looks at whether the full aperture footprint fits inside the shutter opening. Check your shutter width measurement — it's the straight-line width of the gap, not the arc length along the dome.
Yes. Enable "Use a custom wall shape" in the Building Shape card. You can describe any convex building footprint as up to 6 walls, each with its own angle from North and distance from center.
"Offset from pivot" is how far along the main axis from the mount's RA/Dec pivot to that scope's mounting point — this goes into the swing-radius calculation. "Lateral offset" is how far to the side the scope sits — this goes into the telescope-vs-telescope collision check and the plan-view diagram.
It checks whether each telescope's worst-case distance from the mount's pivot fits within the available clearance in every direction at once — the nearest wall, the floor, and the ceiling. If the swing radius clears in every direction, the telescope can point anywhere without hitting anything.
The exported file uses the same azimuth/altitude format as Stellarium's custom horizon files, and is compatible with NINA's horizon import. It's a plain text file, so it's easy to inspect or edit in any text editor.
If your question isn't answered here, get in touch.