Most sites do not have a flat horizon – there are trees to the east, a roofline to the south. A custom horizon file teaches Astro PM the real skyline so the scheduler never plans imaging into an obstruction.
The .hrz File #
A horizon file is a simple text list of azimuth / altitude pairs describing the obstruction line around the compass. You can produce one with common horizon-measurement tools or by hand from a panorama. Astro PM interpolates between points.
Uploading to a Site #
Attach the .hrz to a site in the Equipment panel. From then on:
- Sky View draws the obstruction line over the star field.
- The scheduler checks every time slot against the horizon at the target’s azimuth – a target behind your oak tree simply is not scheduled until it clears it.
- Target charts reflect the reduced usable window.
The NINA Side #
NINA has its own custom horizon setting (Options → General). Load the same horizon there: the plugin’s nightly schedule build honors NINA’s horizon file, so keeping the two identical guarantees the desktop plan and the observatory plan agree. See Connecting NINA to Astro PM.