Meteor Shower Observed Rate

Start from the zenithal hourly rate (ZHR) and scale it to your site. Supply the radiant altitude, your limiting magnitude, and any sky obstruction to forecast how many meteors per hour you are likely to see.

Zenithal hourly rate (ZHR) published for the meteor shower peak.
Altitude of the shower radiant above the horizon during your session (degrees).
Faintest naked-eye star visible at zenith (sky limiting magnitude).
Percentage of the sky blocked by clouds, trees, or buildings (0–90%).
Population index r describing meteor brightness distribution. Leave blank to assume 2.1.

Examples

  • Perseids with the radiant at 60°, limiting magnitude 6.3, and 10% cloud cover ⇒ 66.57 meteors/hour
  • Geminids at 35° altitude, limiting magnitude 5.0, and 30% obstruction ⇒ 21.29 meteors/hour

FAQ

What is the difference between ZHR and observed hourly rate?

ZHR assumes a perfectly dark sky with the radiant at zenith and zero obstruction. The observed rate rescales that ideal benchmark to your real-world observing geometry and conditions.

How do I measure limiting magnitude?

Use star charts or smartphone apps to find the faintest star you can identify at zenith, or convert sky-quality-meter readings into equivalent magnitudes.

Does the calculator work for daytime meteor radio detections?

No. Radio scatter counts follow different selection effects and should be modelled separately. This tool is tuned for nighttime visual observers.

Additional Information

  • Radiant altitude uses the shower radiant, not the direction individual meteors travel across the sky.
  • Limiting magnitude folds in skyglow, aerosols, and eye adaptation; darker skies yield higher counts.
  • Population index r describes the brightness distribution—larger r values indicate a higher fraction of faint meteors.
  • The model assumes naked-eye visual observing and does not account for video or radio detection boosts.

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