- What is the ICRS?
- What is the ICRF?
- How does the ICRS differ from the FK5 system?
- How does the ICRF differ from the FK5 frame?
- What is the CEO (Celestial Ephemeris Origin, sometimes called the NRO)?
- How was the CEO defined?
- What is the essential characteristic of the CEO?
- How is the CEO used?
- If a different point on the starting equator had been selected for the CEO, what would be changed?
- What is the path of the defined CEO?
- How does the new CIP (Celestial Intermediate Pole) differ from the CEP (Celestial Ephemeris Pole)?
- What information is required to determine the direction to a celestial object from a location on the Earth's surface with the best attainable a priori accuracy?
- How are topocentric angles (hour angle/declination or azimuth/elevation) be derived from X, Y and theta?
