The azimuth and altitude of any celestial body depend on the precise time and date, and on the observer's location.
I live in a suburb of Sacramento, CA, and the time right now is May 7, 2011 at 4:31PM Pacific Daylight Time. Procyon is, at this moment, at an altitude of 52 degrees 36 minutes, and an azimuth of 149 degrees 18 minutes; a little east of south. It is at a distance of 11.41 light years. Like most celestial objects, it tracks to the west at about 4 degrees per minute.
I get this data from the free planetarium program Stellarium, available at stellarium.org. If you download this program and program it with your exact location, you can get up-to-the-second calculations for yourself.
However, we don't generally refer to stars by azimuth and elevation; instead, we use the more common measurements of Right Ascension and Declination, numbers that do not change measurably over the span of a century. According to Wikipedia, Procyon is at:
Right ascension
07h 39m 18.1/17.7s
Declination
+05° 13' 29/20"
azimuth 100 degrees altitude 20 degrees
The point on the horizon that is due west has an altitude of zero and an azimuth of 270 degrees.
An object seen halfway between the horizon and the zenith has an altitude of 45 degrees.An object seen due east of the observer has an azimuth of 90 degrees.
The azimuth and altitude of Sagittarius depend where you are on Earth and the date and time. The altitude can be anything form 0-90, and the azimuth 0-180.
This is probably about the "horizon coordinate system". Or, it's sometimes called the horizontal coordinate system. The system uses "altitude" and "azimuth" as coordinates. The azimuth is normally measured from due North as zero. So, that's the "three reference points", probably. Altitude is the angular height of a star above the horizon. Azimuth is the angle of a star measured along the horizon, from the pole.
azimuth 100 degrees altitude 20 degrees
Azimuth = 315° (True) Altitude = 0
The point on the horizon that is due west has an altitude of zero and an azimuth of 270 degrees.
An object seen halfway between the horizon and the zenith has an altitude of 45 degrees.An object seen due east of the observer has an azimuth of 90 degrees.
Recording the location of a star requires a measurement of altitude, azimuth, and time.
The azimuth and altitude of Sagittarius depend where you are on Earth and the date and time. The altitude can be anything form 0-90, and the azimuth 0-180.
The variation of the apparent azimuth and altitude of everything we see in the sky is the result of Earth's rotation.
The variation of the apparent azimuth and altitude of everything we see in the sky is the result of Earth's rotation.
This is probably about the "horizon coordinate system". Or, it's sometimes called the horizontal coordinate system. The system uses "altitude" and "azimuth" as coordinates. The azimuth is normally measured from due North as zero. So, that's the "three reference points", probably. Altitude is the angular height of a star above the horizon. Azimuth is the angle of a star measured along the horizon, from the pole.
This is probably about the "horizon coordinate system". Or, it's sometimes called the horizontal coordinate system. The system uses "altitude" and "azimuth" as coordinates. The azimuth is normally measured from due North as zero. So, that's the "three reference points", probably. Altitude is the angular height of a star above the horizon. Azimuth is the angle of a star measured along the horizon, from the pole.
This is probably about the "horizon coordinate system". Or, it's sometimes called the horizontal coordinate system. The system uses "altitude" and "azimuth" as coordinates. The azimuth is normally measured from due North as zero. So, that's the "three reference points", probably. Altitude is the angular height of a star above the horizon. Azimuth is the angle of a star measured along the horizon, from the pole.
This is probably about the "horizon coordinate system". Or, it's sometimes called the horizontal coordinate system. The system uses "altitude" and "azimuth" as coordinates. The azimuth is normally measured from due North as zero. So, that's the "three reference points", probably. Altitude is the angular height of a star above the horizon. Azimuth is the angle of a star measured along the horizon, from the pole.