Astronomers dream of nights where thousands of stars dazzle in pitch-black skies with the band of the Milky Way flowing like a great river from one side to another. Alas for most of us this is often just a dream. We live in towns and cities polluted by artificial lighting from streets, building and factories that significantly diminish our view of the night sky.
However, it's not all that bleak as things do seem to be improving. Recently more efficient street lights have been installed in many areas, significantly reducing the amount of light beamed up to the heavens rather than down on the ground. Of course there are always out of town regions, especially forests and mountainous areas, away from the bulk of civilisation where the beauty of the night sky still rules. But have you ever wondered, how dark are your night skies? One way to check is by looking towards the constellation of Pegasus.
Pegasus is the 7th largest constellation in the sky covering an impressive 1,121 square degrees. For Northern Hemisphere observers, it's easily recognisable during the autumn months. The prominent asterism known as "Great Square of Pegasus" dominates the constellation. It's made up of reasonably bright stars between 2nd and 3rd magnitude:
Scheat (β Peg) - mag. 2.44
Markab (α Peg) - mag. 2.49
Algenib (γ Peg) - mag. 2.83
Alpheratz (α And) - mag. 2.07
Strangely not all stars are located in Pegasus. The northeastern star and brightest of the four, Alpheratz, lies in neighbouring Andromeda. For a long time, Alpheratz was considered both a part of Pegasus and Andromeda. Eminent 16th century celestial cartographer Johann Bayer catalogued it as α Andromedae and δ Pegasi in his classic star atlas, Uranometria. Finally, when the official constellation boundaries were drawn up by the International Astronomical Union (IAU) in 1922, Alpheratz was assigned to Andromeda.
Inside the Square
The square of Pegasus is large and the four corner stars easily identifiable. Despite this, there are few easily visible stars inside the square, but many at the fringe of naked eye visibility. Therefore counting the total number of stars inside, is an excellent guide to how dark your skies are.
Limiting Magnitude | Number of naked eye stars visible in the square | Seeing |
---|---|---|
6.5 | 35 | Exceptional |
6.25 | 21 | Excellent |
6 | 13 | Superb |
5.75 | 9 | Very good |
5.5 | 7 | Good |
5.25 | 5 | Above Average |
5 | 4 | Average |
4.75 | 3 | Below Average |
4.5 | 1 | Poor |
≤ 4.00 | 0 | Very Poor |
Great Square of Pegasus - pdf format (credit:- freestarcharts)
Stars inside the Square of Pegasus
Index | Henry Draper Catalogue (HD) | Hipparcos Catalogue (HIP) | Bayer | Flamsteed | RA (J2000) | DEC (J2000) | Visual Mag. | Brighter Than | ||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1 | 220657 | 115623 | Upsilon Pegasi | 68 | 23h 25m 23s | 23d 24m 15s | 4.42 | mag 4.5 | mag 4.75 | mag 5.00 | mag 5.25 | mag 5.50 | mag 5.75 | mag 6.00 | mag 6.25 | mag 6.50 |
2 | 220061 | 115250 | Tau Pegasi | 62 | 23h 20m 38s | 23d 44m 25s | 4.58 | --- | mag 4.75 | mag 5.00 | mag 5.25 | mag 5.50 | mag 5.75 | mag 6.00 | mag 6.25 | mag 6.50 |
3 | 224427 | 118131 | Psi Pegasi | 84 | 23h 57m 46s | 25d 08m 29s | 4.63 | --- | mag 4.75 | mag 5.00 | mag 5.25 | mag 5.50 | mag 5.75 | mag 6.00 | mag 6.25 | mag 6.50 |
4 | 218356 | 114155 | --- | 56 | 23h 07m 07s | 25d 28m 06s | 4.76 | --- | --- | mag 5.00 | mag 5.25 | mag 5.50 | mag 5.75 | mag 6.00 | mag 6.25 | mag 6.50 |
5 | 223768 | 117718 | Phi Pegasi | 81 | 23h 52m 29s | 19d 07m 13s | 5.06 | --- | --- | --- | mag 5.25 | mag 5.50 | mag 5.75 | mag 6.00 | mag 6.25 | mag 6.50 |
6 | 221615 | 116264 | --- | 71 | 23h 33m 28s | 22d 29m 56s | 5.33 | --- | --- | --- | --- | mag 5.50 | mag 5.75 | mag 6.00 | mag 6.25 | mag 6.50 |
7 | 222133 | 116611 | --- | 75 | 23h 37m 57s | 18d 24m 02s | 5.49 | --- | --- | --- | --- | mag 5.50 | mag 5.75 | mag 6.00 | mag 6.25 | mag 6.50 |
8 | 448 | 729 | --- | 87 | 00h 09m 02s | 18d 12m 43s | 5.57 | --- | --- | --- | --- | --- | mag 5.75 | mag 6.00 | mag 6.25 | mag 6.50 |
9 | 218792 | 114449 | --- | --- | 23h 10m 43s | 17d 35m 40s | 5.68 | --- | --- | --- | --- | --- | mag 5.75 | mag 6.00 | mag 6.25 | mag 6.50 |
10 | 224930 | 171 | --- | 85 | 00h 02m 10s | 27d 04m 56s | 5.80 | --- | --- | --- | --- | --- | --- | mag 6.00 | mag 6.25 | mag 6.50 |
11 | 223461 | 117500 | --- | 79 | 23h 49m 39s | 28d 50m 33s | 5.95 | --- | --- | --- | --- | --- | --- | mag 6.00 | mag 6.25 | mag 6.50 |
12 | 218396 | 114189 | --- | --- | 23h 07m 29s | 21d 08m 03s | 5.97 | --- | --- | --- | --- | --- | --- | mag 6.00 | mag 6.25 | mag 6.50 |
13 | 220933 | 115806 | --- | 69 | 23h 27m 40s | 25d 10m 02s | 5.99 | --- | --- | --- | --- | --- | --- | mag 6.00 | mag 6.25 | mag 6.50 |
14 | 166 | 544 | --- | --- | 00h 06m 37s | 29d 01m 17s | 6.07 | --- | --- | --- | --- | --- | --- | --- | mag 6.25 | mag 6.50 |
15 | 221662 | 116307 | --- | --- | 23h 33m 55s | 20d 50m 27s | 6.10 | --- | --- | --- | --- | --- | --- | --- | mag 6.25 | mag 6.50 |
16 | 223755 | 117710 | --- | --- | 23h 52m 23s | 21d 40m 16s | 6.13 | --- | --- | --- | --- | --- | --- | --- | mag 6.25 | mag 6.50 |
17 | 218235 | 114081 | --- | --- | 23h 06m 18s | 18d 31m 04s | 6.16 | --- | --- | --- | --- | --- | --- | --- | mag 6.25 | mag 6.50 |
18 | 224303 | 118048 | --- | --- | 23h 56m 42s | 22d 38m 53s | 6.18 | --- | --- | --- | --- | --- | --- | --- | mag 6.25 | mag 6.50 |
19 | 218935 | 114526 | --- | 60 | 23h 11m 49s | 26d 50m 50s | 6.19 | --- | --- | --- | --- | --- | --- | --- | mag 6.25 | mag 6.50 |
20 | 417 | 716 | --- | --- | 00h 08m 52s | 25d 27m 47s | 6.24 | --- | --- | --- | --- | --- | --- | --- | mag 6.25 | mag 6.50 |
21 | 225276 | 399 | --- | --- | 00h 04m 56s | 26d 38m 56s | 6.25 | --- | --- | --- | --- | --- | --- | --- | mag 6.25 | mag 6.50 |
22 | 222098 | 116592 | --- | 74 | 23h 37m 40s | 16d 49m 32s | 6.26 | --- | --- | --- | --- | --- | --- | --- | --- | mag 6.50 |
23 | 220318 | 115407 | --- | 65 | 23h 22m 41s | 20d 49m 43s | 6.28 | --- | --- | --- | --- | --- | --- | --- | --- | mag 6.50 |
24 | 222683 | 116972 | --- | --- | 23h 42m 44s | 16d 20m 09s | 6.30 | --- | --- | --- | --- | --- | --- | --- | --- | mag 6.50 |
25 | 219310 | 114742 | --- | --- | 23h 14m 36s | 24d 06m 10s | 6.36 | --- | --- | --- | --- | --- | --- | --- | --- | mag 6.50 |
26 | 220288 | 115389 | --- | --- | 23h 22m 29s | 25d 55m 07s | 6.38 | --- | --- | --- | --- | --- | --- | --- | --- | mag 6.50 |
27 | 221394 | 116119 | --- | --- | 23h 31m 43s | 28d 24m 13s | 6.41 | --- | --- | --- | --- | --- | --- | --- | --- | mag 6.50 |
28 | 221493 | 116187 | --- | --- | 23h 32m 29s | 23d 50m 37s | 6.41 | --- | --- | --- | --- | --- | --- | --- | --- | mag 6.50 |
29 | 224758 | 34 | --- | --- | 00h 00m 24s | 26d 55m 05s | 6.43 | --- | --- | --- | --- | --- | --- | --- | --- | mag 6.50 |
30 | 218101 | 113994 | --- | --- | 23h 05m 06s | 16d 33m 46s | 6.43 | --- | --- | --- | --- | --- | --- | --- | --- | mag 6.50 |
31 | 218261 | 114096 | --- | --- | 23h 06m 32s | 19d 54m 39s | 6.44 | --- | --- | --- | --- | --- | --- | --- | --- | mag 6.50 |
32 | 221905 | 116465 | --- | --- | 23h 35m 56s | 24d 33m 40s | 6.44 | --- | --- | --- | --- | --- | --- | --- | --- | mag 6.50 |
33 | 221113 | 115915 | --- | --- | 23h 29m 06s | 23d 02m 53s | 6.45 | --- | --- | --- | --- | --- | --- | --- | --- | mag 6.50 |
34 | 225292 | 410 | --- | --- | 00h 05m 01s | 27d 40m 29s | 6.47 | --- | --- | --- | --- | --- | --- | --- | --- | mag 6.50 |
35 | 219196 | 114686 | --- | --- | 23h 13m 59s | 19d 38m 02s | 6.47 | --- | --- | --- | --- | --- | --- | --- | --- | mag 6.50 |