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17. Rigel (Beta Orionis, Struve 668, double star)
Constellation Orion, also known as the Hunter), magnitude 0.1 / 6.8, separation 9.5”, position angle 202°, RA 05h14m DEC -8°.12’. The primary star, the class B8 supergiant Rigel, is the seventh brightest star in the sky, and it is the brightest star in Orion. In my 8-inch Klevtzov it looks white, but in my 85mm Zeiss reflector, I definitely see a hint of blue. The secondary, using the 8-inch Klevtzov at 166x, also looks bluish-white.

18. Trapezium (Theta Orionis, multiple star)
Constellation Orion (also known as the Hunter), magnitude AB 6.7 / 7.9 and CD 5.1 / 6.7, separation AB 8.8” and CD 13.4”, position angle AB 31° / CD 241°, RA 05h35m DEC -5°23’. This group of blazing young stars, known as the Trapezium, doesn’t need an introduction. The trapezium is a group of four bright white stars at the heart of the Orion Nebula. Even in my 85mm refractor at 30x I can see them as four individual stars, forming a trapezium. The magnitude 5.1 C component stands out from the other three fainter stars in the 85mm reflector. Under a real dark sky, I have seen the E and F component in my 8-inch TAL 200K using medium to high magnifications. This group of stars is just wonderful through almost every telescope.

19. Beta Monocerotis (triple star)
Constellation Monoceros (Unicorn), magnitude 4.7 / 5.2 / 7.1, separation AB 7.3” and BC 2.8”, position angle AB 132° and BC 106°, RA 06h29m DEC -07°02’. Sir William Herschel discovered Beta Monocerotis in 1781, and called it “one of the most beautiful sights in the heavens”, and I can only agree with him. I have been observing this wonderful triple in Monoceros on every possible occasion, just enjoying the view: three almost equally bright stars with the same blue-white color. The A, B and C component form a narrow triangle, and I never found another group of three stars that are so close together, equally bright and of exactly the same color. With my 8-inch telescope I use a magnification of 166x to get a real nice split.

20. Castor (Alpha Geminorum, Struve 1110, triple star)
Constellation Gemini (Twins), magnitude 1.9 / 2.9 / 8.8, separation AB 4.0” and AC 72.5” , position angle AB 68° and AC 164°, RA 07h34m DEC +31°53’. In fact, Castor is a system of six stars. Three of them are visible through amateur telescopes, the A,B and C components. Each of the three visible stars is itself a spectroscopic binary. The faint c-component is in fact a pair of red dwarfs orbiting each other, an eclipsing binary (variable star) designated YY Geminorum. Through my 8-inch telescope at 200x all three components look white.


Image from SkyTools2 by CapellaSoft, click to enlarge!

Posted by Math on 06/09 at 11:34 AM
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