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Mission 11: Cassiopeia and the Double Cluster

November 21, 2009

Mission Objectives: Constellation, Open Cluster, Bright Star

Equipment: Naked eye, Binoculars, Telescope

Required Time: 3 minutes

Instructions: Go outside after dark, face northeast, and look for the sideways W. If you’re not sure which W is which, take a free sky map. The W is Cassiopeia, which lies right smack in the middle of the winter Milky Way.

Cassiopeia is a deep sky wonderland in binoculars and telescopes. There are more star clusters than you can shake a stick at–a decent portable sky atlas will show a dozen or more. Even without an atlas, it’s an awesome area to scan around in with optics of any size.

I have a confession, though. Almost every time I go out to observe in the winter, I give Cassiopeia a quick once-over and then leave. Why? Because there’s an even better pair of clusters lurking over the border of the neighboring constellation, Perseus, and Cassiopeia is such a good pointer that you might think it was put there for that purpose. Follow the inner leg of the shallow half of the W about 2/3 of the way to the next bright star, and you’ll find the Double Cluster, NGC 869 and 884. Keep in mind the effect of sky rotation–by 8:30 PM, Cassiopeia is an M centered over the North Star, and by midnight it’s a sigma to the northwest. Adjust your expectations accordingly.

The Double Cluster is one of the finest objects in the night sky, and almost always makes it onto lists with names like “Top 10 Telescopic Targets”. I’m not going to show you any pictures of the clusters themselves, because this is one place where pictures simply don’t do justice. You’ll have to get out under the night sky and see for yourself.

Once you’ve had your mind blown by the Double Cluster, keep on cruising in the same direction and follow the chain of bright stars to Mirphak, or Alpha Persei, the brightest star in the constellation Perseus. Mirphak is surrounded by a broad field of stars called the Alpha Persei association; it is too big to fit in the field of view of most telescopes (except possibly fast focal ratio, widefield scopes like the Astroscan and StarBlast 4.5), but is instead one of the best binocular targets in the entire sky. Have a look and let me know what you think.

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20 comments

  1. Thanks for the perspective. I’m a rank amateur and you make it sound friendly.


  2. Thanks you make it friendly.


  3. Great: simply and very didactic.


  4. Thanks a lot!!Our friend ,you make me broad my knoewledges as well as my narrow heart. The Universe is Marvelous and unlimited but mankind is small and just like a glimpse in the unlimit of time / space of the universe………..


  5. I can’t wait to do this and keep on cruising down to Mirphak with my binocs on a better night without the clouds. Thanks for contributing this blog. I just found it linked on APOD’s site.


  6. [...] Related Missions: Cassiopeia and the Double Cluster [...]


  7. [...] Related Missions: Cassiopeia and the Double Cluster [...]


  8. [...] I switched over to Cassiopeia and its neighbors. I started with the Double Cluster, which I’d seen umpteen times before but never logged for the Deep Sky Bino Club. And I was [...]


  9. I’m always finding my way down to the double cluster in Perseus when visiting Cassiopeia. It’s such a beautiful site with the right field of view.


  10. [...] We also spotted its two satellite galaxies, M32 and M110, without much trouble. By that time the Double Cluster had cleared the treeline to the north so we spent a few pleasant minutes contemplating that [...]


  11. [...] some of the sky’s most brilliant jewels, such as the Pleiades and Hyades, the Beehive, the Double Cluster, and thousands more, of many sizes, ages, and distances. The Double Cluster photographed by Rob [...]


  12. [...] cruising around the sky. We hit just a handful of showpiece objects–the Andromeda galaxy, the Double Cluster, the Pleiades, Jupiter, and the moon–but we spent some time lingering over each one. It has [...]


  13. [...] that we turned 180, to the northeast, and looked at the Double Cluster (NGC 869/884), the Andromeda galaxy (M31) and one of its satellite galaxies (M32). Then a couple of nice [...]


  14. […] dob. We looked at the Saturn Nebula (NGC 7009), which was not detailed but visibly blue, and at the Double Cluster (NGCs 869 and 884), which was simply […]


  15. […] have waxed poetic about the Double Cluster before (you can find it here). It’s pretty close to a larger, sparser cluster called Stock 2, which is shown is most […]


  16. […] cúmulo doble siempre es un espectáculo gratificante  con prismáticos , incluso, a simple vista desde  lugares […]


  17. […] stars, evidence that they were likely a product of the same star-forming region. Always a rewarding sight in binoculars, the Double Cluster is even visible to the unaided eye from dark locations. Not seen in binoculars […]


  18. […] evidence that they were likely a product of the same star-forming region. Always a rewarding sight in binoculars, the Double Cluster is even visible to the unaided eye from dark locations. Not seen in binoculars […]


  19. […] stars, evidence that they were likely a product of the same star-forming region. Always a rewarding sight in binoculars, the Double Cluster is even visible to the unaided eye from dark locations. Not seen in binoculars […]


  20. […] هستند. این خوشه‌ی دوتایی همیشه منظره‌ی رضایت‌بخشی در دوربین‌های دوچشمی دارد، حتی در مکان‌هایی تاریک با چشم غیرمسلح هم رویت […]



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