[OzEclipse (Joe Cali)]

Steve,

You possibly saw an American article. It won't be in Cancer until much later - around midday on the 27th our time. The Cancer just after dark reference must be relating to the USA. We'll see it in the constellations of Hydra and Puppis during the night of the 26th. It travels from just north of M48 in Puppis towards M93 in Hydra during our dark hours.

Topocentric coordinates are the position of the asteroid against background stars as seen from your position on the Earths surface.

Geocentric coordinates are are the position of the asteroid against background stars as seen from the centre of the Earth.

For distant asteroids like those in the asteroid belts between Mars and Jupiter, there is no practical difference. For Near Earth Objects (NEO's) parallax error causes differences in the apparent position even between cities along the east coast.

The attached diagram illustrates the effect. Position C is the centre of the Earth (Geocentric) Pos A and D show very different apparent positions because of their different locations. Pos B lies on the geocentric line and experiences no parallax shift from the geocentric position but only for an instant. During the night, the Earth's rotation moves it off this line and the position once again experiences parallax shift.

DA14 was very close to Earth so this difference was particularly large. This asteroid is a little further out so that differences along the coast are not so extreme.

Hope this clears it up a little.

Joe