Observation Notes:
This double star presented an interesting color contrast compared to the actual spectra. The primary appeared pale yellow, with a fainter blue-gray companion. The primary is F6V, which is believable, but according to the 13th General Catalogue of MK Spectral Classification (Buscombe 1998), the secondary is a K0V star, which should appear yellow-orange if anything. Eric Graff noted White and Yellowish for the pair while using a 150 mm f/6 newtonian at 120X. Alain Gerard recorded pale yellow and yellow-orange. However, as with my observation, Jeff Burton noted pale yellow and blue while using a 203 mm SCT at 111X.
I estimated PA at 10 degrees and separation appeared to be 1/7 of the field of view, or about 100 arcseconds. The actual values are 4.1 degrees and 65.7 arcseconds.
| Subject | Tau1 Hydrae (HJ 1167) |
| Classification | Double Star |
| Position (J2000) | Hydra [RA: 09:29:09 / Dec: -02:46:08]* |
| Position Angle* | 4.1° (1991) |
| Separation* | 65.7″ (1991) |
| Magnitudes* | 4.6 / 7.8 |
| Spectral Types* | F6V / K0V |
| Date/Time | MAR 15, 2007 – 11:50 PM MST (MAR 16, 2007 – 06:50 UT) |
| Observing Loc. | Cinder Hills Overlook – Sunset Crater National Monument, AZ |
| Instrument | Orion SVP 6LT Reflector (150 mm dia./1200 mm F/L) |
| Eyepieces/Mag. | 10 mm + 2X Barlow (240X) |
| Conditions | Mostly clear, calm |
| Seeing | 4/10 Pickering |
| Transparency | NELM Mag ~6.0 |
| References | The Washington Visual Double Star Catalog, 1996.0 (Worley+, 1996); Tycho Double Star Catalogue (TDSC) (Fabricius+ 2002); 13th General Catalogue of MK Spectral Classification (Buscombe 1998) |
*Based on published data.