Double Star Program

Progress: 68/100 features observed (68%)

The Astronomical League’s Double Star Program introduces observers to 100 of the best double and multiple star systems in the heavens. This program is forgiving and doesn’t require dark or moonless skies, making it perfect for less-than-perfect nights and light-polluted areas.

Official AL Program: Double Star Observing Program

Program Requirements

Observe 100 designated double and multiple star systems
Use any telescope with 60mm or larger objective (originally designed for 3-inch refractor)
Record: date, time, latitude/longitude, power(s) used, seeing, transparency, and instrument
Sketch each pair showing relative magnitudes, spacing, and orientation (N and E or W marked)
Estimate position angle within ~20 degrees of accepted value
Identify primary (brighter) star in each system
Note colors and describe splitting difficulty (optional but encouraged)

Complete Double Star List

Below are all 100 double stars in the program, organized by the month when they are best visible in the evening sky (around 9 PM):

November Evening Sky (R.A. 0h - 2h)

Eta Cassiopeiae - 00h 49m.1, +57° 49' (13.4") ✓ Observed
65 Piscium - 00h 49m.9, +27° 43' (4.4") ✓ Observed
Psi 1 Piscium - 01h 05m.6, +21° 28' (29.8")
Zeta Piscium - 01h 13m.7, +07° 35' (22.8") ✓ Observed
Gamma Arietis - 01h 53m.5, +19° 18' (7.4") ✓ Observed
Lambda Arietis - 01h 57m.9, +23° 36' (37.3") ✓ Observed

December Evening Sky (R.A. 2h - 4h)

Alpha Piscium - 02h 02m.0, +02° 46' (1.9") ✓ Observed
Gamma Andromedae - 02h 03m.9, +42° 20' (9.6") ✓ Observed
Iota Trianguli - 02h 12m.4, +30° 18' (4.0") ✓ Observed
Alpha Ursa Minoris - 02h 31m.8, +89° 16' (18.4") ✓ Observed
Gamma Ceti - 02h 43m.3, +03° 14' (2.0") ✓ Observed
Eta Persei - 02h 50m.7, +55° 54' (28.7") ✓ Observed
Struve 331 - 03h 00m.9, +52° 21' (12.0") ✓ Observed
32 Eridani - 03h 54m.3, -02° 57' (6.9")

January Evening Sky (R.A. 4h - 6h)

Chi Tauri - 04h 22m.6, +25° 38' (19.4")
1 Camelopardalis - 04h 32m.0, +53° 55' (10.4")
55 Eridani - 04h 43m.6, -08° 48' (9.3")
Beta Orionis - 05h 14m.5, -08° 12' (9.7") ✓ Observed
118 Tauri - 05h 29m.3, +25° 09' (4.6")
Delta Orionis - 05h 32m.0, -00° 18' (56.2") ✓ Observed
Struve 747 - 05h 35m.0, -06° 00' (36.3")
Lambda Orionis - 05h 35m.1, +09° 56' (4.3") ✓ Observed
Theta 1 Orionis - 05h 35m.3, -05° 23' (Multiple) ✓ Observed
Iota Orionis - 05h 35m.4, -05° 55' (12.5") ✓ Observed
Theta 2 Orionis - 05h 35m.4, -05° 25' (52.3") ✓ Observed
Sigma Orionis - 05h 38m.7, -02° 36' (Multiple)
Zeta Orionis - 05h 40m.8, -01° 57' (Multiple)
Gamma Leporis - 05h 44m.5, -22° 27' (95.5")
Theta Aurigae - 05h 59m.7, +37° 13' (4.2")

February Evening Sky (R.A. 6h - 8h)

Epsilon Monocerotis - 06h 23m.8, +04° 36' (12.2")
Beta Monocerotis - 06h 28m.8, -07° 02' (Multiple)
12 Lyncis - 06h 46m.2, +59° 27' (8.9")
Epsilon Canis Majoris - 06h 58m.6, -28° 58' (7.9")
Delta Geminorum - 07h 20m.1, +21° 59' (5.5")
19 Lyncis - 07h 22m.9, +55° 17' (13.8")
Alpha Geminorum - 07h 34m.6, +31° 53' (5.5") ✓ Observed
k Puppis (HR2948) (not Kappa) - 07h 38m.8, -26° 48' (9.9")

March Evening Sky (R.A. 8h - 10h)

Zeta Cancri - 08h 12m.2, +17° 39' (6.2")
Iota Cancri - 08h 46m.7, +28° 46' (30.7") ✓ Observed
38 Lyncis - 09h 18m.8, +36° 48' (2.6")

April Evening Sky (R.A. 10h - 12h)

Alpha Leonis - 10h 08m.4, +11° 58' (179.2") ✓ Observed
Gamma Leonis - 10h 20m.0, +19° 50' (4.7") ✓ Observed
54 Leonis - 10h 55m.6, +24° 45' (6.8") ✓ Observed
N Hydrae (17 Crateris) - 11h 32m.3, -29° 16' (9.6")

May Evening Sky (R.A. 12h - 14h)

Delta Corvi - 12h 29m.9, -16° 31' (24.2") ✓ Observed
24 Comae Berenices - 12h 35m.1, +18° 23' (20.2")
Gamma Virginis - 12h 41m.7, -01° 27' (3.0") ✓ Observed
32 Camelopardalis - 12h 49m.2, +83° 25' (21.8")
Alpha Canum Venaticorum - 12h 56m.0, +38° 19' (19.5")
Zeta Ursa Majoris - 13h 23m.9, +54° 56' (Multiple) ✓ Observed

June Evening Sky (R.A. 14h - 16h)

Kappa Bootis - 14h 13m.5, +51° 47' (13.8") ✓ Observed
Iota Bootis - 14h 16m.2, +51° 22' (39.0") ✓ Observed
Pi Bootis - 14h 40m.7, +16° 25' (5.4") ✓ Observed
Epsilon Bootis - 14h 45m.0, +27° 04' (2.8") ✓ Observed
Alpha Librae - 14h 50m.9, -16° 03' (231.1") ✓ Observed
Xi Bootis - 14h 51m.4, +19° 06' (5.2") ✓ Observed
Delta Bootis - 15h 15m.5, +33° 19' (105.0") ✓ Observed
Mu Bootis - 15h 24m.5, +37° 23' (109") ✓ Observed
Delta Serpentis - 15h 34m.8, +10° 32' (4.0")
Zeta Corona Borealis - 15h 39m.4, +36° 38' (6.3") ✓ Observed

July Evening Sky (R.A. 16h - 18h)

Xi Scorpii - 16h 04m.4, -11° 22' (7.2") ✓ Observed
Struve 1999 - 16h 04m.4, -11° 27' (11.9") ✓ Observed
Beta Scorpii - 16h 05m.4, -19° 48' (13.4") ✓ Observed
Kappa Herculis - 16h 08m.1, +17° 03' (27.0") ✓ Observed
Nu Scorpii - 16h 12m.0, -19° 28' (41.3") ✓ Observed
Sigma Corona Borealis - 16h 14m.7, +33° 52' (7.2") ✓ Observed
16/17 Draconis - 16h 36m.2, +52° 55' (Multiple) ✓ Observed
Mu Draconis - 17h 05m.3, +54° 28' (2.6") ✓ Observed
Alpha Herculis - 17h 14m.6, +14° 23' (5.0") ✓ Observed
Delta Herculis - 17h 15m.0, +24° 50' (13.7") ✓ Observed
36 Ophiuchi - 17h 15m.3, -26° 36' (5.1") ✓ Observed
Omicron Ophiuchi - 17h 18m.0, -24° 17' (10.8") ✓ Observed
Rho Herculis - 17h 23m.7, +37° 09' (4.1") ✓ Observed
Nu Draconis - 17h 32m.2, +55° 11' (62.1") ✓ Observed
Psi Draconis - 17h 41m.9, +72° 09' (29.6") ✓ Observed

August Evening Sky (R.A. 18h - 20h)

40/41 Draconis - 18h 00m.2, +80° 00' (18.7") ✓ Observed
95 Herculis - 18h 01m.5, +21° 36' (6.4") ✓ Observed
70 Ophiuchi - 18h 05m.5, +02° 30' (6.6") ✓ Observed
Epsilon Lyrae - 18h 44m.3, +39° 40' (Multiple) ✓ Observed
Zeta Lyrae - 18h 44m.8, +37° 36' (43.7") ✓ Observed
Beta Lyrae - 18h 50m.1, +33° 22' (45.7") ✓ Observed
Struve 2404 - 18h 50m.8, +10° 59' (3.6")
Otto Struve 525 - 18h 54m.9, +33° 58' (45.4") ✓ Observed
Theta Serpentis - 18h 56m.2, +04° 12' (22.4")
Beta Cygni - 19h 30m.7, +27° 58' (34.6") ✓ Observed
57 Aquilae - 19h 54m.6, -08° 14' (36.3")

September Evening Sky (R.A. 20h - 22h)

31 Cygni - 20h 13m.6, +46° 44' (Multiple) ✓ Observed
Alpha Capricornus - 20h 18m.1, -12° 33' (381.2") ✓ Observed
Beta Capricornus - 20h 21m.0, -14° 47' (205.4") ✓ Observed
Gamma Delphinus - 20h 46m.7, +16° 07' (9.0")
61 Cygni - 21h 06m.9, +38° 45' (31.8") ✓ Observed
Beta Cephei - 21h 28m.7, +70° 34' (13.5") ✓ Observed
Struve 2816 - 21h 39m.0, +57° 29' (Multiple)
Epsilon Pegasi - 21h 44m.2, +09° 53' (143.9") ✓ Observed

October Evening Sky (R.A. 22h - 0h)

Xi Cephei - 22h 03m.8, +64° 38' (8.1") ✓ Observed
Zeta Aquarii - 22h 28m.8, -00° 01' (2.4") ✓ Observed
Delta Cephei - 22h 29m.2, +58° 25' (41.0") ✓ Observed
8 Lacerta - 22h 35m.9, +39° 38' (22.3")
94 Aquarii - 23h 19m.1, -13° 28' (12.1")
Sigma Cassiopeiae - 23h 59m.0, +55° 45' (3.1") ✓ Observed

Observation Techniques

Equipment Recommendations

Minimum 4" telescope for most pairs
6" or larger recommended for close pairs
Long focal length
High-quality eyepieces
Stable mount for high magnification

Splitting Techniques

Use highest useful magnification
Look for elongation before clean split
Use averted vision for faint companions
Try different eyepieces and magnifications
Be patient - some pairs require calm seeing conditions