1. What Astronomers Measure

2. Where is it? The sky appears as a 2-dimensional sphere
"What good are Mercator's North Poles and Equators
Tropics, Zones, and Meridian Lines?"
So the Bellman would cry, and the crew would reply
"They are merely conventional signs"
L. Carroll -- The Hunting of the Snark
The sky appears as a 2-dimensional sphere
Celestial Coordinates
Ecliptic Coordinates
Galactic Coordinates
Alt-Az Coordinates

3. When is it? Time keeping is tied to the Earth and the Sun
The times of your lives…
Time keeping is tied to the Earth and the Sun
Local solar time
Civil time
Universal time
Sidereal time
Second: the duration of 9,192,631,770 periods of the radiation corresponding to the transition between two hyperfine levels of the ground state of 133Cs
Day: 86,400 seconds
Julian day: days elapsed since 12UT on 4713BC 1 January

4. How Bright is it?
Photometry
Spectroscopy