Frequently asked questions

Swiss Ephemeris > Printable Ephemeris

1. What is the difference between GMT and UT?
   
   There is no difference between GMT (Greenwich Mean Time) and UT (Universal Time), GMT is just an older name.
   
   
2. What does Delta T = [number] mean?
   
   Delta T indicates the difference between UT and TDT (Terrestrial Dynamic Time), which used to be called 'Ephemeris time' in the last century. While UT is not a uniform time scale (it is occasionally adjusted, due to irregularities in the Earth's rotation), TDT is a uniform time scale which is needed as an argument for mathematical theories of celestial movements.
   
   
3. Do you offer a printable sidereal ephemeris?
   
   No, we don't. We have little interest in 'sidereal astrology' and would not know which guru's ayanamsa to choose. They have all different ones and fight a lot about it. You can create a simple sidereal ephemeris on the Swiss Ephemeris test page, if you study all the options.
   
   
4. Trying to access one of the ephemerides for new planets / asteroids, the page gets stuck. Why is that?
   
   This is most likely a bug in the Internet Explorer. It displays long text data tables very slowly. You may have to wait up to 3 minutes for the page to display, and it finally will.