**Exercise:**

From
St.Andrews, at 6 pm on 1998 February 2nd,

the Moon appeared at
altitude +39°, azimuth 196°,

while Saturn is at altitude
+34°, azimuth 210°.

How far apart did the two objects
appear?

The difference in azimuth is 14°.

Use the cosine rule:

cos MS
= cos MZ cos ZS + sin MZ sin ZS cos Z = 0.98

so MS = 12.3°

Which was further east?

The Moon is further east, and higher up, than Saturn.

Back to "the alt-az system".