thanks in avance

and let it sit for as long as you want the trails to be?

i think you'd also want to focus on the north star. not sure what else you'd want to know.

is there any damage to the sensor that occurs from such long exposures?

otherwise you put it in bulb and it stays open as long as you hold down the button

as far as damage... no. If you're taking shots of the sun, yes... but more distant stars, no.

well, if you're in bulb you can do it for as long as you can hold down the button, but if you're holding the button you're probably introducing camera shake which defeats the purpose.
wired remotes are like $5 on ebay.

<ul><li><a href="http://cgi.ebay.com/8m-Infrared-Remote-Control-Canon-Digital-Rebel-XT-XTi_W0QQitemZ170110801887QQihZ007QQcategoryZ64345Q QrdZ1QQcmdZViewItem">http://cgi.ebay.com/8m-Infrared-Remote-Control-Canon-Digital-Rebel-XT-XTi_W0QQitemZ170110801

i have the wired one which has different controls.

Mouseover the <a href="http://www.astropix.com/HTML/C_SPRING/URSAS.HTM">image</a>. Check <a href="http://www.physics.ucla.edu/~huffman/finddip.html">this one</a>, too.

and the other stars circle around it.
pretty sure that's the case at least.

I'm saying that for really long trails, shoot a portion of the sky away from the North star.