IEEE Spectrum breed · Technology

Amateur Astronomers Can Measure Asteroids Via Occultations

Amateur astronomers can contribute to understanding asteroids by observing occultations, where an asteroid blocks the light of a distant star. This method allows for the measurement of asteroid shapes, even with modest equipment.

An asteroid occultation occurs when an asteroid blocks a star's light, casting a shadow on Earth. Amateurs can measure this shadow to map the asteroid's shape, even if it's only a few hundred meters wide and moving at high speeds.

The telescope size needed doesn't scale with asteroid size. A 5.1-inch telescope and a $150 mount with motors are examples of suitable equipment.

An inexpensive color camera ($260) for video rates is recommended. Cameras with large sensors like Sony's IMX585 offer a wide field of view. A cheaper monochrome option is the ToupTek G3M662M.

Predicting occultations is crucial and can be done using free software from the International Occultation Timing Association (IOTA). Accurate time calibration of observations is necessary.

A 'flasher' tool, an LED pulsed by a GPS receiver's second signal, calibrates image timing to milliseconds. The flasher can be controlled to suppress flashes during the occultation.

DIY flashers use a GPS module, Arduino Nano, and other components to drive an LED. The Arduino controls when flashes occur, allowing for calibration pulses at the start and end of recording sessions.

Past observations include a 4 km wide asteroid and a 120 km wide asteroid. The 12 km wide asteroid Duccio was observed moving at 24 km/s, providing excellent time resolution.

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