{"version":1,"generatedAt":"2026-10-28T10:38:56.207Z","kind":"greatest-elongation","name":"Mercury at greatest western elongation, 21 Apr 2025","at":"2025-04-21T18:50:00.000Z","planets":[{"name":"Mercury","magnitude":0.42}],"place":{"ra":0.327,"dec":-0.6,"frame":"J2000","raUnit":"hours","decUnit":"degrees"},"degreesFromSun":27.4,"sky":"morning","elongationDeg":27.4,"litFraction":0.46,"visibility":{"longitude":0,"timeZone":"UTC","twilightSunAltitude":-6,"bands":[{"latitude":60,"verdict":"lost","summary":"It is below the horizon whenever the sky is dark","best":{"at":"2025-04-22T03:30:00.000Z","altitude":-6.6,"azimuth":79,"sunAltitude":-6.4}},{"latitude":45,"verdict":"lost","summary":"Lost in the horizon's haze: 1° up at best once it is dark","best":{"at":"2025-04-22T04:30:00.000Z","altitude":1.4,"azimuth":92,"sunAltitude":-6.3}},{"latitude":30,"verdict":"low","summary":"Low: 8° up in the E at 05:00; a clear, flat horizon needed","best":{"at":"2025-04-22T05:00:00.000Z","altitude":8.4,"azimuth":95,"sunAltitude":-6.2}},{"latitude":15,"verdict":"clear","summary":"12° up in the E at 05:10","best":{"at":"2025-04-22T05:10:00.000Z","altitude":11.9,"azimuth":94,"sunAltitude":-8.2}},{"latitude":0,"verdict":"clear","summary":"17° up in the E at 05:30","best":{"at":"2025-04-22T05:30:00.000Z","altitude":17.4,"azimuth":90,"sunAltitude":-7}},{"latitude":-15,"verdict":"clear","summary":"19° up in the E at 05:40","best":{"at":"2025-04-22T05:40:00.000Z","altitude":19.3,"azimuth":85,"sunAltitude":-7.5}},{"latitude":-30,"verdict":"clear","summary":"19° up in the E at 05:50","best":{"at":"2025-04-22T05:50:00.000Z","altitude":19.4,"azimuth":79,"sunAltitude":-7.9}},{"latitude":-45,"verdict":"clear","summary":"19° up in the ENE at 06:10","best":{"at":"2025-04-22T06:10:00.000Z","altitude":19.2,"azimuth":70,"sunAltitude":-6.7}}]},"links":{"page":"https://www.whatthestar.com/planets/mercury-greatest-elongation-2025-04-21","map":"https://www.whatthestar.com/explore?ra=0.327&dec=-0.6&fov=40&t=2025-04-21T18%3A50%3A00.000Z"},"sources":[{"name":"P. Bretagnon and G. Francou, VSOP87, the planetary theory the map draws, held to JPL’s DE441 within about an arcsecond over 1900–2100","url":"https://www.whatthestar.com/credits#method-planets"},{"name":"U.S. Naval Observatory and Sea and Sky’s Astronomy Calendar of Celestial Events: the dates and angles the tests hold these to","url":"https://aa.usno.navy.mil/data/"},{"name":"A. Mallama and J. Hilton (2018) and the Astronomical Almanac’s phase-angle series: the planets’ magnitudes","url":"https://www.whatthestar.com/credits#method-planets"},{"name":"J. Meeus, Astronomical Algorithms, ch. 25: the Sun, for the twilight each latitude is judged in","url":"https://www.whatthestar.com/credits#method-sun"}]}