How to find Cygnus constellation

The Cygnus constellation at the latitude of Moscow can be observed in full or in part all year round. The best time interval for observing Cygnus is from June to October, when the constellation is in the evening near the zenith.
The Cygnus constellation is one of the few constellations that are easily recognizable by the characteristic pattern of bright stars (Fig. 1).
However, when you first get acquainted with the Cygnus constellation, it is best to start its search based on the well-known constellation Cassiopeia (Fig.12):

Fig. 12. How to find the Cygnus constellation using Cassiopeia stars.

If you mentally draw a line from Rukba (δ Cas) to Navi (γ Cas) and continue it to the stars of the Cygnus constellation, you get the exact hit in α Cyg, Deneb (red line).
The second well-aimed shot is obtained if you draw the line Rukba - Kaf (β Cas) and measure further five more rays of this length, the arrow of the latter rests against the star Algeneb (yellow line).
And there’s one, though not the most convenient option: if you draw a line from Ahird (η Cas) through Caf (β Cas) and beyond , then it will lead to δ Cyg, Favaris (green line).

To successfully search for Cygnus stars, one more remarkable property can be used: starting from the latitude of St. Petersburg and to the south up to the Northern Tropic (from 60.9° to 27.5°), the constellation Cygnus passes through the zenith during the culmination.
The line of the southern meridian is within the constellation for more than 2.5 hours, therefore, to determine the time when Cygnus is at its zenith, it is better to use the table of exact dates of the culmination of the brightest star Deneb, which is located almost in the center of the constellation.

The average local time of the culmination Deneb (α Cyg) in the night sky by season

                                                                                                                                                                                                                                                                                                                                                        

Spring		Summer		Autumn		Winter
Date	Time	Date	Time	Date	Time	Date	Time
March 1	10:05	June 1	03:57	September 1	21:57	December 1	16:00
March 15	08:10	June 15	02:58	September 15	20:57	December 15	15:00
April 1	07:55	July 1	02:00	October 1	19:55	January 1	13:53
April 15	07:05	July 15	01:05	October 15	18:59	January 15	12:58
May 1	06:00	August 1st	23:57	November 1	17:52	February 1	11:51
May 15	05:07	August 15	23:00	November 15	16:58	February 15	10:55

 

Since the duration of the year is not an integer number of days, the deviation from the data given in this table can lie within ± 5 minutes, which is completely irrelevant for our purposes. Most importantly, the table shows that the constellation Cygnus makes sense to search at the zenith only from July to November.

Now it remains only to correctly determine the angular dimensions of the Cygnus constellation. In Fig. 14, the constellation is presented in that position, so it can be seen overhead on a summer or autumn evening, turning south, southeast or southwest.

Fig. 14. Estimation of the angular size of the Cygnus constellation with outstretched arm.

The angular distance between the brightest stars of Cygnus from Deneb to Sadr is 6 ° 08 ', from Deneb to Favaris approximately 10 °. The angular distance between the thumb and index finger of the outstretched arm of a person of normal physique is 16-18 ° (regardless of gender and age from 7 years), thus, the stars of the Cygnus against the background of an outstretched arm will look approximately as shown in Figure 14.

 

Sergey Ov (Seosnews9): Созвездие Лебедь