Epsilon Hydrae (Struve 1273)

Observation Notes:

This was a great double to observe. The primary is a bright, third magnitude pale yellow star with a much fainter seventh magnitude, blue-gray companion resting right up against it. When the seeing was choppy, this secondary disappeared into the overpowering wash of yellow. I thought it looked a bit like a little bluebottle fly sitting on the edge of a fluttering sunflower.

PA appeared to be about 315°. The first diffraction rings seemed to be barely in contact, which indicated a separation of 2.5 to 3 arcseconds. According to the Washington Double Star Catalog, the primary is itself comprised of 2 stars of magnitudes 3.8 and 5.3. The period of the very close AB pair is 15.05 years, and the AB-C period is 890 years.

Subject Epsilon Hydrae (STF 1273)
Classification Double Star
Position (J2000) [RA: 08:46:46.1 / Dec: +06:25:09]*
Position Angle* AB-C=195° (1825)
AB-C=271° (1959)
AB-C=292° (1994)
Separation* AB-C=3.2″ (1825)
AB-C=3.1″ (1959)
AB-C=3.0″ (1994)
Magnitudes* A=3.8; B=5.3; AB=3.6; B=7.8
Spectral Types*
Date/Time OCT 22, 2006 – 3:55 AM MST (OCT 22, 2006 – 10:55 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 Clear, calm

Seeing 5/10
Transparency NELM Mag 6.8+
References The Washington Visual Double Star Catalog, 1996.0 (Worley+, 1996), Visual Double Stars in Hipparcos (Dommanget+, 2000) via VizieR

*Based on published data.