Plane-Parallel Airmass Estimate

How to use this tool

1. Estimate atmospheric path length relative to the zenith at moderate altitude.
2. Set object altitude in the indicated units.
3. Calculate and compare relative airmass, zenith angle.

Try this example

{
  "alt": 30
}

Accuracy and scope

Secant approximation only; restricted to altitudes of at least 15°. Does not model refraction or weather.

Is my data uploaded?

This tool runs locally in your browser. Input and output are not sent to a processing server. Copy or download your result before leaving the page.