Hi Chris,
An introduction to astronomy is usually included in the curriculum of most year 11 and 12 physics courses.
I know that is certainly true in NSW today.
One of the most useful introductions to astronomy is the study of the
discovery of the laws of motion and the series of observations that
lead to the realization that the Sun is at the center of the Solar System.
That narrative of an understanding of the motion of the heavens, starting
with Plato and Ptolemy then onto Copernicus and Tycho Brahe, then onto
Kepler and Galieo and culminating in Newton's inverse square law not
only provides a wonderful insight into the workings of nature but also
into the workings of the modern scientific process, plus it is a fascinating
story.
That narrative certainly use to be what was taught in NSW for year 11 & 12
students undertaking physics.
So I would recommend investigating suitable texts that cover that
part of the physics curriculum.
The good news is that it then dovetails with what will be taught next year.
Back in the 70's when I studied high school physics, these were the first two
texts :-
*
Concepts of Motion, Text and Handbook Volume 1
*
Motion in the Heavens, Text and Handbook Volume 2
One of the experiments even included building your own telescope, which is described in the second text starting on page 151.
You might find newer texts that provide essentially the same narrative,
but history being what it is, the story hasn't changed.