April Lyrids

A ZHR of 18 is modest — roughly one meteor every three minutes at best, before any correction for radiant altitude or sky brightness. What makes the Lyrids worth it is position: the radiant is at declination +33.4°, so from the northern mid-latitudes it climbs to 78°, close enough to overhead that you lose very little to the sine correction. If your sky is dark and the Moon is out of the way it is a pleasant hour; if either is compromised, the low base rate leaves nothing to spare.

It depends on your latitude, and the two are opposites. The Lyrid radiant is at +33.4° declination and the eta-Aquariid radiant at −0.5°, essentially on the celestial equator. From 45°N the Lyrid radiant reaches 78° while the eta-Aquariid radiant barely clears 45°; from 30°S the eta-Aquariids are the better proposition by a wide margin. The eta-Aquariids also carry a ZHR of 50 against the Lyrids' 18, so anywhere south of about 20°N the choice is not close.

Outbursts are real and documented: on 22 April 1982 the Lyrid ZHR rose to about 90 over roughly 40 minutes, with United States observers reporting short-lived rates equivalent to 250 per hour during a burst of about 15 minutes. Comparable displays were recorded in 1803 and 1922, which is where the often-quoted 60-year spacing comes from — a pattern, not a schedule. This site does not predict them and says so on the methodology page. The rate model takes the tabulated ZHR as a constant and corrects it for radiant altitude, Moon, twilight and cloud; modelling a dust-trail encounter needs the parent body's ejecta streams integrated forward, which is outside this engine's scope. If an outburst is forecast elsewhere, treat the numbers here as a floor rather than a ceiling.

Of 2026 to 2030, 2028 put the peak within a quarter-lit Moon. 2027 land near full. Because the Lyrid ZHR is only 18, moonlight hurts this shower disproportionately: there is no surplus of bright meteors to push through a lit sky.

The parent body is Comet C/1861 G1 (Thatcher), on a very long orbit, so the stream is old and well mixed. Practically that means the geocentric velocity of 46.6 km/s and the population index of 2.1 are stable year to year — the shower behaves the same way each April, which is why the year-to-year decision comes down almost entirely to the Moon.

Judged only on how much of the Moon is lit at the peak instant: 2026 — 22 April 2026 (Moon 36% lit); 2027 — 23 April 2027 (Moon 95% lit); 2028 — 22 April 2028 (Moon 6% lit); 2029 — 22 April 2029 (Moon 58% lit); 2030 — 22 April 2030 (Moon 71% lit). The dark-Moon years are 2028; the washed-out ones are 2027. Moon illumination is the only one of the four factors that is knowable years ahead — cloud cover is not, and neither is whether you will be somewhere dark.

Because 18 is the zenithal hourly rate: what one observer would count under a magnitude 6.5 sky with the radiant straight overhead. Two corrections pull it down before you ever look up. Rate scales with the sine of the radiant altitude, so a radiant 30° up delivers half of what it delivers at the zenith. And the population index for this shower is r = 2.1, which means each magnitude of sky brightness you lose costs you a factor of 2.1 in the count. A suburban sky two magnitudes shallower than the reference therefore divides the rate by about 4.4. Real counts are typically 30–50% under the modelled figure even after those corrections.