What is an ephemeris?
An ephemeris is a daily table of where each celestial body sits in the zodiac. For every date it lists a sign and a degree from 0 to 29, so you can follow a planet's exact path through the month.
Astronomers and astrologers have used ephemeris tables for centuries. Before software, they were printed in thick annual volumes; this tool computes the same positions on demand for any month.
How to read the table
Each row is a day of the month and each column is one of the ten bodies, from the Sun through Pluto. A cell shows the degree within the sign followed by a three letter sign code, such as 12 Tau for twelve degrees of Taurus.
Slow planets barely move from day to day, while the Moon can cross more than twelve degrees in a single day. Watch a column downward to see a body approach the end of a sign and then change into the next one.
Reading retrograde motion
When a planet is retrograde, its degree decreases from one day to the next instead of increasing. In this table those days are flagged so you can spot a retrograde phase at a glance.
Retrograde motion is an optical effect caused by the changing angle between Earth and the other planet. The body does not truly move backward, but from our viewpoint it appears to retrace its steps for a while.