| With an angular separation of 13.4", this fairly bright pair is easy to split with just about any telescope. Their magnitudes are 4.5 and 6.6. Their orbital period is estimated to be over 6000 years. The name Asellus Tertius means "third donkey colt", and with the naked eye it forms a small triangle with two other dim stars (Asellus Primus and Asellus Secundus, the other two donkey colts). |
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| Evening visibility: |
March-October |
| Best viewed with: |
telescope |
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Printable chart (pdf) |
View larger image |
Directions:
Start by finding the Big Dipper, one of the most recognizable star patterns in the sky. It is part of the constellation Ursa Major, the big bear. It is shown here upside down, high in the sky above Polaris, which is where it can be found during the evenings in spring and summer. For other seasons and times of night, rotate the chart as needed to match what you see in the northern sky.
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| Note that north is to the bottom in this chart. Find Mizar, the middle star in the handle of the Big Dipper, and Alkaid, the star at the end of the handle. As shown in the chart below, Kappa (κ) Bootis forms a right triangle with Mizar and Alkaid. It will be dim to the naked eye but easily seen in binoculars or a finderscope. Note that this star is part of a small triangle of three dim stars (called Asellus Primus, Asellus Secundus, and Asellus Tertius, the three donkey colts). |
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| Star charts created with Cartes du Ciel |
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