Long exposures on Canon 7D
 

Can someone please tell me how to set long exposure times ( minutes or hours) on the Canon 7D
Thanks

Set the mode dial to manual, adjust the exposure speed to bulb and then take your exposure. If you have a remote this will be easier (a timer remote or one that can lock the shutter open), otherwise you will have to hold the shutter button down for the duration of the exposure.

correct but in additon I have found with things like star trails if you go too long then noise becomes an issue.I got around it by taking sequential shots and then stacking .

On a 50 d just set motordrive to continuous ......lock on bulb and set exposure times .

@Matt: Any recommendations on stacking software?

You could try CombineZM or Helicon Focus, or the Auto-Align/Auto-Blend options in Photoshop CS (they're in the edit menu, but you'll need to create a layer stack first, and select all the layers to make these auto options active). If it's just for star trails (as opposed to using it to maximise depth of field in a series of macro images), simply create a layer stack of all the source files in Photoshop (to do this in Bridge go to Tools > Photoshop > Load Files into Photoshop Layers) and then change the blending layer of every layer apart from the base layer to Lighten...