Exercise:

The four stars at the corners of the “Great Square of Pegasus” are:

Calculate the lengths of the two diagonals of the “Square”.

It is necessary to plot the four stars, at least approximately,
to find out which pairs form the diagonals!

Then, to find the length of each diagonal, use the cosine rule:
cos S₁S₂ = cos S₁P cos S₂P + sin S₁P sin S₂P cos P

This gives α And to α Peg = 20.1°
and β Peg to γ Peg = 20.5°.

Back to "the RA-dec system".