Struve 2306

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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)