Tuesday, September 11, 2007

the dippers

from the northern hemisphere, you can easily spot the big dipper... and figure out which direction is north! as you can see from the map below, the big dipper is close to the horizon right now. the stars in the handle are bright and easy to find.

follow the handle to the dipper and find the stars "merak" and "duhbe" (pronounced "doobie"!). following these stars with your eyes from merak thru duhbe takes you in a nearly straight line to polaris... the "north star". while all stars rise in the east and set in the west... just like the sun... the north star stays stationary in our sky and all other stars rotate around it. thats why long exposure night time images when you use no tracking mechanism look like this...

that is an extreme example that was exposed for 11 hours!!!! but the effect of the long star trails is cool.

once you find polaris, you can try to identify the little dipper knowing that polaris is the last star in the handle of the little dipper. the stars are fainter so i always have a much harder time finding the little one, but it's a good challenge for a non-cloudy night and hopefully you can always determine which way is north!!


Chris said...

Orion is also usually visible, even in cities. While not as useful for navigation, it's easy to impress people by pointing up and saying"look, there's Orion."

One the of things I miss the most about living in the mountains is not being able to see the Milky Way on a clear evening.

For those of you out there who want to make your own star trail pictures, it's real easy to do short trails with a digital camera. Just put your camera on a tripod, then take multiple long exposures (30 seconds each?). The images can be combined in photoshop to create one long star trail. You're only limited by the size of your memory card and your patience to stay up and trip the shutter release.

Peregrine said...

Thanks for this. I was never able to find Polaris, because I'd always thought you were supposed to follow the handle of the big dipper, not the stars on the cup. So either I misunderstood it, or the guy explaining it to me was an idiot. Probably a little of both. It all makes sense now.

Also, knowing that there's a star pronounced "Doobie" makes me exceedingly happy.

At my parent's place, away from the city, the big dipper is usually seen just above the tree line on the way up on the hill. Here in the city, the night sky is just red/purple with occasional stars here and there. That is, when there isn't fog.

Chuck said...

So how do I find this star using the Southern Cross?


Russ said...

Amazing image! did you take this photo yourself? I just wanted to know the camera settings... 11 hour exposure, what f stop?

Anonymous said...

What F stop??

The lens was "WFO" as we say in the movie business,
Wide the Fuck Open, (suggesting that infinity requires no depth of field, so to get the most light on the film, one would not stop the lens down at all).

Best Wishes!