Mapping the Milky Way's Invisible Hydrogen | 24-Hour Timelapse | 2 July 2026 | DEC +19.3°

Full 24-hour drift scan of the 21 cm neutral hydrogen line captured on 2 July 2026 from Aquila Radio Observatory. A 2.4 m parabolic dish + Airspy SDR observes continuously as Earth rotates, sweeping the fixed beam across a strip of sky at DEC +19.3°, capturing HI emission from two galactic arm crossings and a Sun transit all in one day. SETUP • Dish: 2.4 m parabola on Alt-Az mount • Receiver: Airspy Mini + LNA chain • Center frequency: 1420.4058 MHz (21 cm HI rest line) • Bandwidth: 3 MHz · 1024 channels • Integration: 300 s per obs · 281 obs / day • Software: Virgo + custom Python pipeline WHAT YOU'RE SEEING • Top left - current calibrated HI spectrum (dB above cold sky) • Top right - cumulative waterfall building up through the day • Bottom - sky trace on real optical panorama, showing dish beam position colored by HI intensity THE PHYSICS Two bright peaks appear as the Earth rotates: • ~RA 19-20h - Cygnus/Aquila galactic-arm crossing (early in the day) • ~RA 5.5h - Perseus spiral arm / anti-centre region (later - peak +1.57 dB) ☉ SUN TRANSIT Around 13:17 IST the Sun passes through the beam. You'll see a brief compression / broadband bump - the Sun's continuum lifting the noise floor. It's real physics, not RFI. #RadioAstronomy #HydrogenLine #21cm #Amateurscience #GalacticHI #DIYtelescope #SDR #Airspy 0:00 Midnight start (day begins) 0:26 Cygnus/Aquila arm crossing 2:20 Perseus arm approach 2:35 Sun transit 4:40 End of day