Asteroid Florence Makes a Close Approach to Earth

3122 Florence is a stony trinary asteroid of the Amor group. It is classified as a near-Earth object (NEO) and potentially hazardous object (PHO). It measures approximately 3 miles in diameter. It orbits the Sun at a distance of 93 – 232 million miles once every 2 years and 4 months (859 days). 

On the 1st of September, 2017, Florence passed at a distance of 4,391,000 miles from Earth (approximately eighteen times the average distance of the Moon). This is the asteroid's closest approach since 1890 and the closest until after 2500.

On September 3rd I was able to image Florence through my 4" William Optics Apo Refractor.  Here are two images: one is a time lapse movie showing the movement of Florence against the star field. This sequence is sped up to show the asteroid's relative motion (Florence's actual movement rate across the sky was about 0.336 degrees per hour - a pretty hefty clip).

Florence's relative motion in the sky
Rate is 120x actual

 The second image shows the asteroid's position every 60 seconds of time.

Annotated Chart showing Florence's march from south (bottom) to north (top)
Chart spans 1.0 x 1.2 degrees