July 12, 2007
Mu Bootis (Struve 28 / 1938)
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Observation Notes:
I wasn't prepared for what a pleasant surprise this 'double' star was at high magnification when the B star turned out to be a close double itself. The yellow primary appeared to be separated from the BC combo by about 120 arcseconds. The actual value is 108.4. I estimated the main PA at about 164°, with an actual value of 171°.
The BC combo appeared purplish-blue, and were close enough that their first diffraction rings intersected each other, but did not intersect the diffraction discs. This works out to a separation of about 2.2 arcseconds. Their PA appeared to be from 0 to 10°. When I first checked the WDS Catalog, I was momentarily frustrated to see 1.3 arcseconds and 327 degrees. But then I realized that was a measurement from 1826 on a very close pair. It turns out their orbital period is 246 years. The actual 2007.3 values calculated from Brian Workman's calculator are 2.25 arcseconds and 6.2°.
| Subject | Mu Boötis (A-BC: STF 28 / BC: STF 1938) |
| Classification | Multiple Star |
| Position (J2000) | Boötes [RA: 15:24:29.3 / Dec: +37:22:38]* |
| Position Angle* | A-BC: 171° (1834); BC: 6.2° (2007.3) |
| Separation* | A-BC: 108.4" (1834); BC: 2.25" (2007.3) |
| Magnitudes* | A: 4.3 / B: 7.2 / C: 7.8 / BC: 6.5 |
| Spectral Types* | A: F0V / BC: G0V |
| Date/Time | APR 29, 2007 - 12:40 AM MST (APR 29, 2007 - 07:40 UT) |
| Observing Loc. | Flagstaff, AZ (Home) |
| Instrument | Orion SVP 6LT Reflector (150 mm dia./1200 mm F/L) |
| Eyepieces/Mag. | 10 mm + 2X Barlow (240X) |
| Conditions | Mostly clear, slightly breezy, nearly full moon |
| Seeing | 5-6/10 Pickering |
| Transparency | NELM Mag ~5.0 |
| References | The Washington Visual Double Star Catalog, 1996.0 (Worley+, 1996); Catalogue of Stellar Spectral Classifications (Skiff, 2005) |
Posted by Jeremy at July 12, 2007 11:35 PM .
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