Alpha Crucis

Marcos Valério Mataratzis
Star: Alfa Crucis
Date & Time: 05/03/2004, 7:00 PM UT
Seeing: 7 <1-10 Seeing Scale (10 best)>
Transparency:  <1-10 Scale (10 best)>
Location of site: Rio de Janeiro, Brazil
(Lat 22°54´ S, 43°14´ W)
Site classification: Suburban
Conditions:
Temperature: 27°C
Humidity: 70%
Sky darkness: 5.0 <Limiting magnitude> 
Telescope: 83mm refractor (f/14.7) Magnification: 78x, 102x, 163x, 203x
 

Brightest star of this constelation, 13ª brightest star in heavens, 1,400x brighter than our sun, this triple system lies at 271 LY from us. AB components are B1 blue stars, 1.3 and 2.3 magnitude, 4.0" appart at 114°. There is also a C component 89.8" appart at 204°. This C star is a B5 also blue 4.9 magnitude.

Easy system to split at moderate power. I started at 78x. At this power I could saw an elongated AB companions and a far away C. at 102x the main pair was splitted. Higher magnification just makes space between A and B bigger.
 

 


Eddy O'Connor
Star: Alfa Crucis
Date & Time: Wednesday, May 12th 2004
9-10.30 local; UT +9.
Seeing: 8/10 (10 best)
Transparency: 9/10 (10 best)
Location of site: Terara, New South Wales
Australia, Long.150º.38;
Dec. S 34º.52.
Site classification: Suburban
Weather:
Sky darkness: ---  <Limiting magnitude> 
Telescope: 8" Newt. F9
Eyepieces: 10mm Plossl,18mm Ultima Celestron, 32 mm Teleview Plossl
Magnification:
Harshaw Scale: -1! (1-5; 1 best).

Unfortunately, this star marking the foot of the Cross just carries the mundane name Acrux, when it deserves Bellissima at least!

A stunning pair that I use to line up my finderscope every night I view. In the finderscope the close pair look like a single brilliant star and the wide third star looks a  Deep Blue binocular object. In the telescope field the dazzling Pearl-like pair are just separated in good seeing while the third star in the field is a delicate pale contrasting  onlooker.
  

Luis Balanzino
Star: Alfa Crucis
Date & Time: May 9 2004, 1h to 3h UT
Seeing: 7 <1-10 Seeing Scale (10 best)>
Transparency: 7 <1-10 Scale (10 best)>
Location of site: Cordoba, Argentina
31.400S, 64.183W
Site classification: Urban area
with considerable light pollution
Conditions: Temperature: 10º C
Moon: in Sagittarius illuminated
fraction 0.76
Sky darkness: 4 <Limiting magnitude> 
Telescope: ETX-90 Maksutov-Cassegrain (90mm f/13.8) mounted on Velbon
photo tripod
Eyepieces: 26mm Meade Super Plossl, 18mm Celestron Ultima Plossl,
12.5mm TAL Plossl, 2X TAL Barlow
Magnifications: 48x, 69x, 100x, 200x
 

The most representative southern constellation, Crux is plentiful of interesting objects, between them Alpha Crux (Acrux), the 12 th. brightest star in the sky and the closest 1 st. magnitude star to the south celestial pole.

Alpha Crux is also a splendid triple. The farther component (C) is bright and bluish, 90" away and easily visible in binoculars and finders. So at low power, the star looks like a delicate double. Then at higher magnification, the brighter component splits in two close, very bright and bluish components. This bright pair has slightly closed from the first Dunlop's measurements in 1826.

In my telescope, they can be split barely at 69x, and very clearly at 100x. At 200x, they look like very bright dots of bluish light, well separated and with the distant C component still in the field.
Needless to say, this is one of the very best doubles in the sky, and one of my favourites sights.

 

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