9th February

Asteroid 2018 BC was discovered on Sunday 4th February 2018,
and was predicted to fly past the Earth at only 39000 miles, or 1/5th the distance to the Moon.
I used the Minor Planet Ephemeris generator to determine where it should be from my location
and set up a series of 20 second exposures. The ASA DDM60 mount provided accurate pointing
and the asteroid whizzed through the field of view exactly on time.
These animations show two series of images:

How accurate is the ephemeris at predicting asteroid positions?
To generate an ephemeris you need to input accurate geographic coordinates and the altitude of the observatory for near Earth asteroids.

This picture shows how phenomenally accurate the ephemeris is: