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Tools / Moon tracker and EME planner

Moon tracker and EME planner

Live moon azimuth and elevation for your location, with everything you need for moonbounce (EME): path loss, Doppler, sun distance, and when the moon is up for both you and a DX station over the next two weeks.

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Optional
From your device
Moon direction now––
EME path loss––
Echo Doppler––
Phase––
Declination––
Moon windows, next 24 hours––

Moon elevation, next 24 hours (UTC)

You DX station

14-day EME planner

Date (UTC)MoonriseMoonsetHighestDecPath loss (dB)From sunLitShared window

Days when the moon is within 15° of the sun are greyed out, because solar noise makes EME very difficult. All times are UTC.

How EME works

Earth-moon-earth (EME), or moonbounce, uses the moon as a passive reflector. Signals travel about 770,000 km there and back and lose around 252 dB on 2m, so EME needs a good antenna, a low-noise preamp and a little power. Digital modes such as JT65 and Q65 in WSJT-X have made it possible with a single long Yagi and 100 to 500 W on 2m, and big stations can work each other on CW.

What makes a good EME day

  • Distance: the moon's distance changes by about 12% over a month, so the path loss varies by around 2 dB, with the lowest loss at perigee.
  • Distance from the sun: when the moon is near the sun, around new moon, solar noise swamps the echoes.
  • Sky noise: the moon passing in front of the galactic plane adds noise, which matters most on 2m and below.
  • Declination: for northern stations, a high positive declination keeps the moon up longer and gives longer windows to Europe, North America and Asia.

The planner shows the path loss, sun distance and shared window for each day so you can pick the best time for a sked.

Doppler

As the Earth turns, you move towards or away from the moon, which shifts your echo by up to about ±300 Hz on 2m and ±3 kHz on 23cm. The Doppler figure is for your own echo. When working another station, their Doppler adds to yours, so set your receiver accordingly or let WSJT-X track it for you.

Accuracy

The moon's position is worked out in your browser with a standard astronomical method, accurate to about a tenth of a degree, and corrected for your position on Earth and for refraction. That's well inside the beamwidth of even a large EME array. For the sun and other satellites, see the grey line map and the satellite pass predictor.

Questions

What is the EME path loss on 2m?

About 251 to 253 dB, depending on the moon's distance. On 23cm it's about 271 dB.

Can I do EME with a small station?

Yes, on 2m with a single long Yagi, a mast-head preamp, 100 to 500 W and the Q65 or JT65 modes. Listening for the big stations' signals is a good first step.

Why is the moon's position different from a sky app?

Apps often give geocentric positions. This tracker corrects for your position on Earth, which shifts the moon by up to a degree.

When is the best time for EME?

Near perigee, with the moon well away from the sun and, on 2m, away from the galactic plane. Weekends with good conditions are announced by EME groups.