Double stars
NGC7000.COM
Double, multiple and special stars
by Jean Vallières

Observation and photography of double and multiple stars is a project open to all amateur astronomers, even with modest instruments. Moreover, this type of project is virtually unaffected by light pollution as may be the pictures of deep sky objects.

The sight of two close stars of different colors remains a great show to watch. The best known example is Albireo (beta Cygni), but the sky is filled with dozens of other easily observed multiple stars.

All images were captured with a modified RCX400 telescope of 250 mm aperture and 2000 mm focal length, and with a small Celestron NexImage 5 Planetary Camera. The small 2.2 microns pixels of this camera have yielded a good resolution without requiring a barlow or eyepiece projection.

To properly represent the stellar pairs, the images are all at the same scale and measure for most 80 x 80 arcsec (slightly less than 2 times the apparent diameter of Jupiter). Each image is a combination of the eight best 1/15 s unitary shots (out of 80 to 160 frames), aligned and combined with Registax. I tried to process the images to reproduce as closely as possible the apparent observed colors, using PixInsight software and PhotoShop. The photo series was started in June 2012 and should be completed as conditions will allow. The celestial north is up (unless otherwise stated).

The stars shown can be observed until at least two months before and after the month indicated.

Click on the name of the star for a location map.
NAME 1 NAME 2 Note R.A. 2000.0 Decl. 2000.0 Magn. 1 Magn. 2 Separation (B-V) 1 (B-V) 2 Colors
mu Dra     17h 05m 20.2s +54° 28' 13" 5.6 5.6 2.2" 0.44 0.45 yellow  -  yellow
alpha Her Rasalgethi   17h 14m 38.9s +14° 23' 25" 3,4 5.3 4.9" 1.29 0.67 orange  -  blue green
rho Her     17h 23m 41.0s +37° 08' 45" 4.5 5.4 4.1" -0.02 0.00 white  -  light blue
nu Dra     17h 32m 10.6" +55° 11' 03" 4.9 4.9 62" 0.25 0.28 cream  -  cream
psi1 Dra     17h 41m 56.3s +72° 08' 58" 4.6 5.7 30.3" 0.39 0.49 light yellow  -  yellow
61 Oph     17h 44m 34.1s +02° 34' 46" 6.1 6.5 20.6" 0.08 0.06 white  -  white
95 Her     18h 01m 30.4s +21° 35' 45" 4.9 5.1 6.4" 0.11 0.86 light green -
yellow orange
70 Oph     18h 05m 27.2s +02° 30' 09" 4.3 6.2 6"     yellow  - orange
100 Her     18h 07m 49.6s +26° 06' 04" 5.8 5.9 14" 0.15 0.12 white  -  white
epsilon1 Lyr   1 18h 44m 20.4s +39° 40' 12" 5.0 6.0 2.6" 0.12 0.28 white  -  white
epsilon2 Lyr   1 18h 44m 22.8s +39° 36' 45" 5.2 5.4 2.3" 0.17 0.21 white  -  white
zeta Lyr     18h 44m 46.6s +37° 36' 18" 4.3 5.7 44" 0.19 0.29 white  -  cream
beta Lyr Sheliak 2 18h 50m 04.8s +33° 21' 46" 3.7 V 6.7 46" -0.10 -0.03 white  -  white
omicron Dra     18h 51m 12.1s +59° 23' 18" 4.6 8.1 34.2" 1.19 1.18 yellow orange  -  green
theta Ser     18h 56m 13.2s +04° 12' 13" 4.6 5.0 22.3" 0.16 0.20 white  -  white
Notes:
1 : The third star, 16 Dra, of magn. 5.5, is 90" to the south of 17 Dra. Color light blue and (B-V) =  -0.06.
NAME 1 NAME 2 Note R.A. 2000.0 Decl. 2000.0 Magn. 1 Magn. 2 Separation (B-V) 1 (B-V) 2 Colors
kappa Boo     14h 13m 29.0s +51° 47' 24" 4.5 6.6 13.6" 0.19 0.35 white  -  blue
ksi Boo     14h 51m 23.3s +19° 06' 02" 4.7 6.8 6.9" 0.70 1.16 yellow  -  orange
May
June
NAME 1 NAME 2 Note R.A. 2000.0 Decl. 2000.0 Magn. 1 Magn. 2 Separation (B-V) 1 (B-V) 2 Colors
delta Ser     15h 34m 48.2s +10° 32' 20" 4.1 5.1 3.9" 0.24 0.24 light yellow  - light yellow
zeta CrB     15h 39m 22.7" +36° 38' 09" 5.0 5.9 6.4" -0.10 -0.10 light blue  -  green blue
kappa Her     16h 08m 04.6s +17° 02' 49" 5.0 6.2 27" 0.91 1.12 yellow  -  orange
sigma CrB     16h 14m 41.1s +33° 51' 32" 5.5 6.5 6.2" 0.55 0.58 yelloe  -  yellow
17 Dra   1 16h 36m 13.7s +52° 55' 28" 5.4 6.4 3.4" -0.06 0.05 light blue  -  white
July
August
Notes:
1: Epsilon1 and epsilon2 themselves form a separate pair of 208 " that is called the Lyrae double-double.. Epsilon1 is the most northerly.
2: Beta Lyrae is an eclipsing variable star whose magnitude varies from 3.3 to 4.3 with a period of 12.94 days.
Notes:
1: Struve 2470 and Struve 2474 form themselves a pair separated by 10.4 arc minutes and are known as the other double-double in Lyra. The difference with Epsilon Lyrae is that the stars are smaller but more separated and all of different colors.
2: The double star Albireo is the best known and most observed colored double star. The colors are visible even with binoculars.
See also:
NAME 1 NAME 2 Note R.A. 2000.0 Decl. 2000.0 Magn. 1 Magn. 2 Separation (B-V) 1 (B-V) 2 Colors
15 Aql     19h 04m 57.7s -04° 01' 53" 5.4 7.0 38" 1.12 1.48 yellow  -  yellow orange
Struve 2470 SAO 67870 1 19h 08m 45.2s +34° 45' 37" 7.0 8.4 13.4" -0.13 0.05 blue  -  white
Struve 2474 SAO 67879 1 19h 09m 04.4s +34° 36' 00" 6.7 8.0 16.2" 0.61 0.73 yellow  -  dark yellow
beta Cyg Albireo 2 19h 30m 43.3s +27° 57' 35" 3.4 5.5 34.4" 1.09 -0.10 gold  -  blue
16 Cyg     19h 41m 49.0s +50° 31' 30" 6.0 6.3 39.6" 0.64 0.66 yellow  -  yellow
psi Cyg     19h 55m 37.8s +52° 26' 20" 5.0 7.5 2.9" 0.10 0.29 white  -  white
57 Aql     19h 54m 37.7" -08° 13' 38" 5.7 6.5 35.5" -0.08 -0.04 yellow  -  blue
31 Cyg     20h 13m 37.9s +46° 44' 29" 3.8 7.0 107" 1.27 -0.13 yellow  -  blue
gamma Del     20h 46m 39.5s +16° 07' 27" 4.2 5.0 9.0" 1.00 0.53 yellow  -  blue green
September
NAME 1 NAME 2 Note R.A. 2000.0 Decl. 2000.0 Magn. 1 Magn. 2 Separation (B-V) 1 (B-V) 2 Colors
61 Cyg     21h 06m 54.0s +38° 44' 58" 5.2 6.1 34.2" 1.07 1.31 orange  - red
Struve 2816 (Cep)   1 21h 38' 57.6" +57° 29' 21" 5.7 7.5
7.5
11.8"
20.1"
0.15 0.18
0.15
all white
mu Cyg     21h 44m 08.6s +28° 44' 34" 4.7 6.1 1.8" 0.41 0.52 yellow  -  yellow
ksi Cep     22h 03m 47.5" +64° 37' 41" 4.4 6.4 6.9" 0.31 0.48 yellow  -  yellow
delta Cep     22h 29m 10.3s +58° 24' 55" 4.1 6.3 41" 0.78 -0.03 yellow  -  blue purple
zeta Aqr     22h 28m 49.9s -00° 01' 12" 4.3 4.5 2.2" 0.38 0.34 light yellow  -  yellow
Notes :
1 : Struve 2816 is a triple star inside the nebula IC 1396.