Exercise:

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

star

R.A.

declination

α And

00h 08m

+29°05'

β Peg

23h 04m

+28° 05'

α Peg

23h 05m

+15° 12'

γ Peg

00h 13m

+15° 11'


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".