Tau-1 Hydrae (HJ 1167)

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.

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