# Find sidereal time and azimuth of Deneb (a Lebed) at the moment when he is in Petersburg at an altitude of 48

**Find sidereal time and azimuth of Deneb (a Lebed) at the moment when he is in Petersburg at an altitude of 48о on the eastern part of the horizon**

The latitude of Petersburg is 60o, so the PP1 world axis will make an angle of 60o with the midday SN line. The declination of a Cygnus b = + 45o. Draw a parallel line KL at a distance of 45o from EQ and a parallel line GN at a distance of 48o from SN; their intersection will give us point D. On the straight line GH and on the straight line KL, as on diameters, we draw semicircles. From point D draw lines DM1 perpendicular to GH and DM2 perpendicular to KL until they intersect with the corresponding semicircles.

Now you only need to connect the points M1 and M2 with the corresponding centers R and F and measure the angles with a protractor: PGRM1 = A = 107o and РKFM2 = t = 287o = 19h8m.

Thus, we have determined the azimuth and hour angle of the star. Right ascension a Cygnus is known, and we find it from the table a = 20h39m; therefore, the sought sidereal time is s = t + a = 19h8m + 20h39m = 15h47m