4 Centauri (Herschel 51)

Observation Notes:

After a blustery evening attempting to observe at Cinder Hills Overlook (Sunset Crater National Monument), I gave 4 Centauri a try. At low power, this double appeared to have a cream colored primary and a blue-gray secondary. At 240X however, the color of the primary appeared to be an aqua color instead. I checked with Eric Graff, who was observing with me through the relentless gusts, and he noticed the same high power vs low power color effect on this double through his scope (a 6″ f/6 Parks Astrolight). PA appeared to be 190° with a separation of 20 arcseconds. WDS values are 185° and 14.9 arcseconds. Spectral types are B5V / A3V, so the high power view was the most accurate for color estimation.

Subject 4 Centauri (H 51)
Classification Double Star
Position (J2000) Centaurus [RA: 13:53:12.5 / Dec: -31:55:39]*
Position Angle* 185°
Separation* 14.9″
Magnitudes* 4.78 / 8.45
Spectral Types* B5V / A3V
Date/Time MAY 11, 2007 – 09:45 PM MST (MAY 12, 2007 – 04:45 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, gusty winds
Seeing 3/10 Pickering
Transparency NELM Mag ~6.8
References The Washington Visual Double Star Catalog, 1996.0 (Worley+, 1996); Catalogue of Stellar Spectral Classifications (Skiff, 2005)

*Based on published data.