Photographing Star Trails

Ok, I am going camping at Lake Powell next week and I want to try to do a star trails picture. I have been doing some reading about it, but I'm still seeking advise. I have a Canon 40D, how long will my battery last, fully charged with the bulb setting. Can I make it to a 30 min exposure? I have seen some pictures with an hour plus exposure. I'm sure I will have to play around with it, and try several times. Do I need to get an AC adapter for my battery? Please help!

I use the same body and have done hour+ exposures with it without a problem and without my extra battery grip. You should be fine. Set it on bulb, open up your aperature, set the ISO to 100 and let it go. Make sure you turn the noise reduction on, the shot will take twice as long, but you'll love the result.

So you used just your canon battery and you had enough juice? I didn't even think about the battery grip.

Another option is taking multiple 30 sec exposures and then stitching them together: http://www.startrails.de/html/software.html

I think I am going to attempt just doing one long exposure first. See how that goes.

With a DSLR you're going to see a lot of noise doing a single exposure for more than a couple of minutes. You can do a dark subtract, but the temperature needs to be a close to the same throughout luminance exposure and the dark exposure.
The closer you can get your camera centered to the polar axis the more dramatic the trails. You'll have small circle trails and progressively larger circle trails as you capture field rotation.
The further from the polar axis the straighter the
trails.. they'll look more like lines rather than circles.

I have read that you should turn your noise reduction off, but then i have also read to keep your noise reduction on. I would think you would want it off especially if you are shooting with a low ISO? Which one do you want, on or off?

I usually leave it off for long exposures, a one hour exposure renders your camera useless for 2 hours.

If you're looking for information to take with you on the road, Popular Photography has a real nice article on night photography in their current (October) issue.

Definitely do the 30-45 second or so pics then stitch them together. They turn out waaay better that way IMHO. You have more control of your background illumination that way. An hour exposure may end up totally blown out if you are not careful. With 30-40 second or so (or even 1 minute exposures) you can preview your background before you spend the night in the cold.

Also, make sure you shoot in raw...otherwise you may be stuck with a darker pic than you like. The last shot was pretty dark straight out of the camera...a little selective exposure boost and it turned out much better. It would have been useless as a JPG. If you can, try and get the sandstone illuminated by the moon. I would love to try and get a startrail that is reflecting off of powell glass.

Here are a couple from Zions

PS--> Bring at least 2 batteries and your charger. I also happen to love fish-eyes for startrails as well.

(Message edited by Bakes5 on September 16, 2009)

Thanks for everyone's advise. We leave today for Powell. I will post pics when i get back, if i'm a bit successful!

Nice work Bakes !