Mission 1: The Summer Triangle

August 16, 2009

Mission Objective: Bright stars

Equipment: Naked eye

Required Time: 1 minute

Instructions: Go outside after sunset and look up. If you do so not long after dark, and you face east, you’ll see three bright stars making a big triangle high in the sky. The brightest star, at the top of the triangle, will be almost directly overhead. This is Vega, in the constellation Lyra. Down and to the left of Vega is Deneb, in Cygnus (off to the northeast if you’re facing east). Down and to the right is Altair, in Aquila. Vega, Deneb, and Altair make up an informal grouping known as the Summer Triangle.

If you live under a lot of light pollution–like I do–you’ll have no problem finding the Summer Triangle because the three stars will be pretty lonely up there. Even if you’re fortunate enough to live under dark skies, the Summer Triangle is easy to spot because its members are so much brighter than anything else in the area.

The Summer Triangle in Stellarium. Click to enlarge.

The Summer Triangle in Stellarium. Click to enlarge.

To get both the Summer Triangle and the horizon in the same shot in Stellarium, I had to zoom out a lot, which introduced some fish-eye distortion. This makes it look like a cozy little polygon high up in the sky. It’s not! When Vega is high overhead, Deneb and Altair are still climbing the eastern sky, and the whole triangle takes up a huge swath of cosmic real estate.

Two more things about the picture above. You can just make out the Milky Way as a band of faint light cutting across the triangle from north to south. The whole area is packed with star clouds and other deep-sky goodies for binoculars and telescopes. And the very bright light near the southeastern horizon is Jupiter, the king of the planets, just rising to begin his stately progression across the southern sky.

But those are missions for other evenings.


  1. done – even got brave and took some shots of Jupiter w/ a telephoto lens. Not much to write home about, but fun nonetheless…

  2. Awesome! Jupiter is one of my all-time favorites, and I’m planning on writing a LOT about it once it gets just a little higher in the evenings.

    I am also a huge proponent of photographic experimentation. I have a long post I need to transfer from my old blog about photographing the moon with a point-and-shoot digital camera and a pair of binoculars. That worked far better than even I expected.

    Thanks for stopping in and commenting. Keep us posted on your further adventures.

  3. Would you lose ALL your remaining respect for me if I told you that I attempted this mission last night and failed? True: I couldn’t find the triangle.

  4. Heck, no! I’m proud of you for trying…and pleasantly surprised that you did.

    Okay, things to check: first, you’re in England. Are you sure it wasn’t cloudy? Vega is bright but not that bright. 🙂

    Seriously, though, you’re a lot farther north than I am, which means that the pole star is higher in the sky and everything else is shifted south. I punched up the just-after-dark sky from southern England in Stellarium and everything is much closer to the zenith than it is here. The picture in the post makes it look like you gaze off to the east to see the triangle. Even here, it’s much more like cranking your head back and looking straight up to find Vega, and looking slight down left and right to pick up Deneb and Altair.

    Also, these directions are for just after dark. If you go outside closer to midnight, everything in the sky will have rotated around to the west. I am torn on whether or not to do a post on sky motions; it would be simpler to just have you fast-forward in Stellarium and see what happens.

    Did you punch this up in Stellarium before you went outside? I know, asking you to do so somewhat defeats the point of having blog posts that supposedly do all the work for you. But I use Stellarium like this all the time. In fact, since the Summer Triangle stars are all bright and you don’t need much dark adaptation to see them, you can put Stellarium into night mode and carry your laptop outside with you.

    It’s worth taking the time to find these, because there are some Summer Triangle goodies coming up in Mission 3. Sadly, Mission 2 is probably out for you, considering your high latitude and that big hill south of your house.

  5. Ooh, snarky! No, it wasn’t a cloudly night. I could see plenty of stars, just not the right ones.

    If I have a chance tonight, I’ll look higher up. Ironically, I am about to go swanning off to Spain for the best part of a fortnight, so I’ll see a noticably different set of stars — still, that ought to make the triangle easier, not harder.

    “Rotated round to the west” — I’m not sure what direction that is, given that the triangle starts out in the east. Do you mean it’s moving to the north or the south?

    I installed Stellarium, but it didn’t work — long wait while it loaded shedloads of data, textures, etc., and then after all the mounting excitement, it seggy-faulted. (That’s like a General Protection Fault, for you Windows people.) I don’t have time to look into this right now.


  6. “Rotated round to the west” — I’m not sure what direction that is, given that the triangle starts out in the east. Do you mean it’s moving to the north or the south?

    Much more south than north. Remember that the stars rise in the east and set in the west, just like the sun, and for the same reason. Everything appears to rotate around the pole star, which is much higher in the sky where you’re at. For someone at the Equator, the stars appear to pass almost directly east to west across the dome of the sky. For someone at the North Pole, the pole star is directly overhead and the stars just make circles in the sky without either rising or setting, except for those very close to the horizon. For those of us in between, the stars (and sun, moon, planets, etc.) rise in the east, arc around southwards, and set in the west, except for the circumpolar stars that are close enough to the pole star to be above the horizon all the time. Much more to say on that another time.

    I installed Stellarium, but it didn’t work — long wait while it loaded shedloads of data, textures, etc., and then after all the mounting excitement, it seggy-faulted. (That’s like a General Protection Fault, for you Windows people.)

    Ah, this must be the vaunted “ease of use” that Mac people are always going on about. Stellarium has a Linux version, and AFAIK you still have a Linux machine, so…hacker, IT thyself! 🙂

    Okay, seriously, I know you’re about to leave on vacation and don’t have time to deal with this right now. As an emergency patch, you could dig out the “Binocular Highlights” book I left last fall, which has good sky maps and ought to cover sky motions at least briefly. If that’s too inconvenient, download the Getting Started in Astronomy guide from Sky & Telescope, print it out (only 12 pp.), and take it with you on vacation.

    You’re right, from Spain you will see many more southern stars and the moon, planets, etc. will be higher in the sky and easier to see. When you do leave and return? I might be persuaded to get some moon/planet posts up early if they’d be of any use to you while you travel.

  7. Oh, and don’t forget to take your binoculars! That’s just good vacation advice, whether you plan on stargazing or not.

  8. Har! It WAS the Linux version. Not tried it on the Mac yet.

    We leave tomorrow, so don’t up the posting rate on my account 🙂

  9. I was going to up the post rate so you could benefit from them while you were traveling, but I don’t blame you for not checking this blog every day while you’re on vacation. (Well, I do blame you, but I forgive you.)

    New moon is in a couple of nights, so in the early evenings watch for the crescent moon low in the west and Jupiter low in the east. And have a good vacation. 🙂

  10. […] Related Missions: Summer Triangle […]

  11. […] “easy reach” means roughly “within ten minutes”). I started out with the Summer Triangle and its associated constellations: Lyra, Cygnus, and Aquila. In Cygnus I stumbled across an open […]

  12. […] Related Missions: Summer Triangle […]

  13. […] find alignment stars, out comes the phone, because with a handful of exceptions–Polaris, the Summer Triangle, the Winter Hexagon, and a few favorite doubles–I don’t know what these darned things […]

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