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The complete Mizar system. Mizar and Alcor are separated by almost 12 seconds of arc and can be distinguished by anyone with good eyesight. Each star is itself a double, and the constituents of Mizar are also doubles. So Mizar is a quadruple star and Alcor is double. The two systems appear to be moving through space together, so it is assumed that they are associated despite their great separation. The faint star, BD+55 1602, is not associated and is simply in the same line of sight.
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A shorter exposure of the same field to show the components of Mizar a little bit more clearly.
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Albireo is β-Cygni. This is easily the best rendition of the colours of this beautiful double star that I have achieved. It was taken with an Olympus C5050 camera attached afocally to a William Optics DCL4337 eyepiece on my LX200. Each of these stars is itself double, and in each case the two components are almost identical in colour and in magnitude. The magnitudes are 3.08 for the orange component and 5.1 for the blue component and they are separated by 33 seconds of arc.
The picture on the left is a stack of five 1-second exposures. The resulting image was enhanced by increasing the saturation to 100%, applying a Gaussian blur of 6-pixel radius, and reducing the size to 25%.
It has been suggested that I over-emphasised the colours by increasing the saturation too much and that the picture does not represent reality. On the right is a single exposure of 0.25 sec, also with the colours enhanced, but if you move your mouse over that image you will see the picture with no enhancement. This is what the camera saw, but my eyes don't see the colours that are really there.
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Algieba is Gamma Leonis. Its two components are both giant stars (10 and 23 times the diameter of the Sun), separated by about 170 AU.
Polaris is the Pole Star, or Alpha Ursa Minor. The brighter component is Polaris itself at magnitude 2.0; the fainter star is designated BD+88 7 and is magnitude 8.2. Polaris itself is double, the primary star is a yellow supergiant and is a Cepheid variable from the period of which its distance can be estimated as 431 light years.
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