Reddit reviews Practical Astronomy with your Calculator

Check out Practical Astronomy with your Calculator and see if that fits your needs. Fantastic book.

When observing stars in the sky, you cannot measure distances between stars in length, only in angles and only in relation to other stars in the sky. Many calculations are made using angles because it's the only accurate measurement of distant objects, but our observation position is constantly moving.

Even this book I have: https://www.amazon.com/Practical-Astronomy-Calculator-Peter-Duffett-Smith/dp/0521356997 doesn't have any reference to Parsec. The name itself is composed from parallax and arc second. Parallax is the observable shift of the object in relation to other objects around it when the observer moves, and arc second which is 1/360 of a turn (360 degrees is a full turn of a circle) divided by 60 minutes divided by 60 seconds: 1/1296000 of a turn