Sunday, May 17, 2009

Rasalgethi -- Head of the Kneeler

Rasalgethi or Alpha Herculis (64 Herculis) located near the border of the constellation Hercules and Ophiucus could be one of the most beautiful double star systems to view in the spring and early summer sky. Alpha 1 is a gorgeous red giant that appears that way in your quality telescope. This star is 400 times the size of our Sun, 300 million km radius or 14 solar masses. At about 70X, you begin to see the star as a pair. Alpha 2 is a yellow giant star. Alpha 2 is also a double star itself, not visible in a backyard telescope.

When seeing permits, you can easily split them at about 140X and see the colour differential. With and easy 4.7 arc second separation, most quality backyard telescopes will find this easy. With a little sky knowledge it's easy to find in the city skyglow.

Quite a sight!


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