What will you
capture tonight?

Windows show time above your altitude limit in the selected darkness and any selected direction. East + South means either sector, not both at once. North covers NW–NE, east NE–SE, south SE–SW and west SW–NW.

Curves share a 0–90° altitude scale and the full-night time axis. Green highlights calculated usable windows; grey also includes blocked directions and elapsed time. The dashed line includes any obstruction profile from Sky Map. Curves below the horizon are clipped at 0°.

Windows use five-minute samples; display curves use ten-minute samples plus window boundaries and the best time. Peaks and boundaries are approximate. The compass uses true north, not your phone heading. Circumpolar means above the horizon all day, not necessarily above your altitude limit. Weather, terrain and moonlight still matter.

Moon phase above is a calendar estimate. Target cards calculate Moon separation and altitude at the target’s best time using the Sky Map engine, in the background. Moon-free windows overlap your usable target windows with the Moon below a level horizon; local terrain and atmospheric glow are not modelled. Narrowband is not immune to moonlight.