Sketch of Delta Serpentis (Struve 1954)
Observation Notes:
Over the last couple hundred years, the stars in this binary system have been moving clockwise in relation to one another by about 50 degrees. The WDS 1782 measurement was 227 degrees at 2.5 arcseconds. I measured 183 degrees with a separation of 3 to 5.5 arc seconds on April 13, 2008. Brian Workman’s DS Calculator shows 175.6 degrees at 4.4 arc seconds for that date. My PA measurement is pretty bad on this one, and I’ll need to come back to it. According to Sissy Haas’ Double Stars for Small Telescopes, the orbital period is 1,038 years. The F class stars should present a yellow color, but I noted a white primary with a blue secondary. Smyth notes: “[sometimes] both have a bluish tinge…against the theory of contrast.”
| Subject | Delta Serpentis (STF 1954) |
| Classification | Double Star (Binary) |
| Position (J2000) | Serpens [RA: 15:34:48.1 / Dec: +10:32:15]* |
| Position Angle* | 183° [2008.3 my measurement] 175.6° [2008.3 Workman Calculator] |
| Separation* | 3 – 5.5″ [2008.3 my measurement] 4.4″ [2008.3 Workman Calculator] |
| Magnitudes* | A: 4.2; B: 5.2 |
| Spectral Types* | A: F0IV; B: F0IV |
| Date/Time | APR 13, 2008 – 12:05 PM MST (APR 13, 2008 – 07:05 UT) |
| Observing Loc. | Flagstaff, Arizona, USA – Home |
| Instrument | Orion Skyview Pro 6LT (150 mm dia./1200 mm F/L) |
| Eyepieces/Mag. | 12 mm Meade Astrometric EP + 2X Barlow (200X) |
| Conditions | Clear, first quarter moon |
| Seeing | 5/10 Pickering |
| Transparency | NELM Mag 5.0 |
| *References | The Washington Visual Double Star Catalog (Mason+ 2001-2009); Catalogue of Stellar Spectral Classifications (Skiff, 2008); Starry Night Pro Plus; Brian Workman Double Star Calculator |