fajr-watch
Turnkey Raspberry Pi appliance that watches dawn and dusk, measures the solar depression angle at true Fajr and Isha, and feeds the observations into prayer time calibration research.
About
Every prayer time algorithm assumes a fixed depression angle for Fajr and Isha, and nobody has measured across latitudes whether those numbers hold. fajr-watch is a Raspberry Pi station that runs unattended: it captures the twilight horizon every 10 seconds, detects when dawn begins and dusk ends, records the exact solar depression angle at each, and uploads the observations. The data feeds pray-calc-ml, which trains the dynamic twilight algorithm used by pray-calc. The repo carries the full bill of materials, the SD card image build script, and a smaller indoor variant built around an ambient light sensor.