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Observation Notes:
Nestled in the rich star fields between the Eagle and Swan Nebulae lies a fascinating multiple star. Struve 2306 was surprisingly colorful for a trio of 8th and 9th magnitude stars. The primary was a strong yellow with a rich blue companion to the southwest. At high power this companion coalesced into a close double itself during moments of good seeing. I measured the A-BC separation at 9.5 arc seconds with a position angle of 221 degrees. This agrees with a 1999 2MASS measurement of 9.57 arc seconds and 221.6 degrees. Measuring the BC pair was very difficult, and I came up with .8 arc seconds and 58 degrees which compares with a 1959 measurement of 1.2 arc seconds and 70 degrees.
| Subject | STF 2306 |
| Classification | Multiple Star |
| Position (J2000) | Scutum [RA: 18:22:14 / Dec: -15:05:17]* |
| Position Angle* |
AB: 221° [2008.5 my measurement]; 221.6° [1999.3 TMA2003 (2MASS Catalog)] BC: 58° [2008.5 my measurement]; 70° [1959 Visual Double Stars in Hipparcos (Dommanget+, 2000)] |
| Separation* | AB: 9.5″ [2008.5 my measurement]; 9.57″ [1999.3 TMA2003 (2MASS Catalog)] BC: .8″ [2008.5 my estimate]; 1.2″ [1959 Visual Double Stars in Hipparcos (Dommanget+, 2000)] |
| Magnitudes* | A: 8.08; B: 8.61; C: 9.00 |
| Spectral Types* | A: K5+II; BC: F5III |
| Date/Time | JUL 3, 2008 – 3:30 AM MST (JUL 3, 2008 – 10:30 UT) |
| Observing Loc. | Anderson Mesa, Arizona |
| Instrument | Orion XT8 (203 mm dia./1200 mm F/L) |
| Eyepieces/Mag. | 10 mm Sirius Plössl + 2X Barlow (240X) 12 mm Meade Astrometric EP + 2X Barlow (200X) |
| Conditions | Partly cloudy, calm |
| Seeing | 6/10 Pickering |
| Transparency | NELM Mag 6.8 |
| *References | The Washington Visual Double Star Catalog, 1996.0 (Worley+, 1996); CCDM (Catalog of Components of Double & Multiple stars (Dommanget+ 2002); Visual Double Stars in Hipparcos (Dommanget+, 2000); Tycho Double Star Catalogue (TDSC) (Fabricius+ 2002); Catalogue of Stellar Spectral Classifications (Skiff, 2007) |