# Ephemeris > An ephemeris is a table of planetary positions over time. What an ephemeris is, how it is computed, and what astrologers use it for. - Page: https://novaoracles.com/glossary/ephemeris - Language: en An ephemeris is a table of where the planets are over time, the reference astrologers use to see what the sky was doing on any date. Traditionally it was a printed book of daily positions. NovaOracles computes its own: a full planetary theory for the planets and a high-precision model for the Moon, with the classical formulas for the ascendant, Midheaven and house cusps. Every position is calculated and checked against professional ephemerides to within a fraction of an arcminute, so your chart and every transit are accurate to the arcminute. An ephemeris is the almanac behind astrology: a table that says where every planet was, is, or will be, day by day. Charts and forecasts all draw on one. Before software, an astrologer kept a printed volume on the shelf and looked positions up by hand. ## A table of positions at set intervals An ephemeris lists the positions of the Sun, Moon and planets at set intervals, most often once every twenty-four hours at a fixed reference time. Each entry gives a body's place along the zodiac as a sign and degree, its ecliptic longitude, and sometimes its latitude and speed. Early ephemerides were built from careful observation and long hand calculation. A modern one is generated from mathematical models of how the solar system moves, which return each planet's position to the arcminute across the span a chart needs. ## From natal chart to transit: where every reading starts The ephemeris is where a reading starts. To draw a [natal chart](https://novaoracles.com/glossary/natal-chart) you take the positions for the birth date and arrange them for the exact time and place. To find a [transit](https://novaoracles.com/glossary/transit), you read the table forward from today and watch for a planet reaching an aspect to a birth placement. For centuries the phrase "check the ephemeris" meant look up the sky. ## Looking up where Mars sat on your birthday Suppose you want to know where Mars sat on your birthday. Open the ephemeris to that date and read off the entry, say Mars at 14 degrees of Leo. Run the same table into next month and you can spot the day a moving planet will reach a sensitive point in your chart. A tool does this in an instant, but the logic is the same lookup. The older printed volumes listed a position only once a day, so an astrologer had to work out the hours in between by hand, a step that software now skips by computing the position for your exact minute. ## Ephemeris, chart and horoscope An ephemeris is not a chart; it is the raw list of positions, while a chart arranges those positions for one moment and place. It is also not a horoscope, which interprets a chart. One practical detail trips people up: an ephemeris is calculated for a set reference time, so a position shifts slightly for your own hour and zone along the [ecliptic](https://novaoracles.com/glossary/ecliptic). ## Positions computed, not copied from a table The NovaOracles [birth chart tool](https://novaoracles.com/tools/birth-chart) computes its own positions rather than copying a printed table, and the [transits guide](https://novaoracles.com/guides/transits) shows how those positions turn into a forecast. ## FAQ ### What is an ephemeris? A table listing where the Sun, Moon and planets sit in the zodiac at regular moments, usually once a day. It is the raw position data behind every chart and transit. ### What is an ephemeris used for? To cast a birth chart for a given moment and to find transits going forward. Look up a date and you can read off each planet's sign and degree for that day. ### How accurate is a computed ephemeris? A modern computed ephemeris is accurate to the arcminute for the planets over the dates a chart needs, far finer than a chart drawn by hand could ever require.